errors: metadata errors refactor

[muzarski]

Ref: #519

Motivation

The goal of this PR is to purge metadata.rs of QueryError, and replace it with MetadataError. Thanks to that metadata related functions are now independent of QueryError.

I tried to split this PR into commits, so each commit handles one function/method from metadata module. New error variants are introduced where necessary.

When it comes to public API - after this PR Session::refresh_metadata() will now return MetadataError.

Pre-review checklist

• I have split my patch into logically separate commits.
• All commit messages clearly explain what they change and why.
• [ ] I added relevant tests for new features and bug fixes.
• All commits compile, pass static checks and pass test.
• PR description sums up the changes and reasons why they should be introduced.
• I have provided docstrings for the public items that I want to introduce.
• [ ] I have adjusted the documentation in ./docs/source/.
• I added appropriate Fixes: annotations to PR description.

[github-actions]

cargo semver-checks detected some API incompatibilities in this PR.
Checked commit: 1d10e56

See the following report for details:

cargo semver-checks output

./scripts/semver-checks.sh --baseline-rev 9441b0593385e6aef6af482334b3ad81fcb7c047
+ cargo semver-checks -p scylla -p scylla-cql --baseline-rev 9441b0593385e6aef6af482334b3ad81fcb7c047
     Cloning 9441b0593385e6aef6af482334b3ad81fcb7c047
    Building scylla v0.15.0 (current)
       Built [  25.547s] (current)
     Parsing scylla v0.15.0 (current)
      Parsed [   0.049s] (current)
    Building scylla v0.15.0 (baseline)
       Built [  22.642s] (baseline)
     Parsing scylla v0.15.0 (baseline)
      Parsed [   0.049s] (baseline)
    Checking scylla v0.15.0 -> v0.15.0 (no change)
     Checked [   0.127s] 127 checks: 125 pass, 2 fail, 0 warn, 0 skip

--- failure enum_missing: pub enum removed or renamed ---

Description:
A publicly-visible enum cannot be imported by its prior path. A `pub use` may have been removed, or the enum itself may have been renamed or removed entirely.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.39.0/src/lints/enum_missing.ron

Failed in:
  enum scylla::errors::ViewsMetadataError, previously in file /home/runner/work/scylla-rust-driver/scylla-rust-driver/target/semver-checks/git-9441b0593385e6aef6af482334b3ad81fcb7c047/62fca62783f2893603c618574acc5e36f91a0e69/scylla/src/errors.rs:546

--- failure enum_variant_missing: pub enum variant removed or renamed ---

Description:
A publicly-visible enum has at least one variant that is no longer available under its prior name. It may have been renamed or removed entirely.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.39.0/src/lints/enum_variant_missing.ron

Failed in:
  variant PeersMetadataError::SystemPeersInvalidColumnType, previously in file /home/runner/work/scylla-rust-driver/scylla-rust-driver/target/semver-checks/git-9441b0593385e6aef6af482334b3ad81fcb7c047/62fca62783f2893603c618574acc5e36f91a0e69/scylla/src/errors.rs:455
  variant PeersMetadataError::SystemLocalInvalidColumnType, previously in file /home/runner/work/scylla-rust-driver/scylla-rust-driver/target/semver-checks/git-9441b0593385e6aef6af482334b3ad81fcb7c047/62fca62783f2893603c618574acc5e36f91a0e69/scylla/src/errors.rs:459
  variant MetadataError::Views, previously in file /home/runner/work/scylla-rust-driver/scylla-rust-driver/target/semver-checks/git-9441b0593385e6aef6af482334b3ad81fcb7c047/62fca62783f2893603c618574acc5e36f91a0e69/scylla/src/errors.rs:446
  variant ProtocolError::InvalidCqlType, previously in file /home/runner/work/scylla-rust-driver/scylla-rust-driver/target/semver-checks/git-9441b0593385e6aef6af482334b3ad81fcb7c047/62fca62783f2893603c618574acc5e36f91a0e69/scylla/src/errors.rs:333
  variant TablesMetadataError::SchemaTablesInvalidColumnType, previously in file /home/runner/work/scylla-rust-driver/scylla-rust-driver/target/semver-checks/git-9441b0593385e6aef6af482334b3ad81fcb7c047/62fca62783f2893603c618574acc5e36f91a0e69/scylla/src/errors.rs:527
  variant TablesMetadataError::SchemaColumnsInvalidColumnType, previously in file /home/runner/work/scylla-rust-driver/scylla-rust-driver/target/semver-checks/git-9441b0593385e6aef6af482334b3ad81fcb7c047/62fca62783f2893603c618574acc5e36f91a0e69/scylla/src/errors.rs:531
  variant UdtMetadataError::SchemaTypesInvalidColumnType, previously in file /home/runner/work/scylla-rust-driver/scylla-rust-driver/target/semver-checks/git-9441b0593385e6aef6af482334b3ad81fcb7c047/62fca62783f2893603c618574acc5e36f91a0e69/scylla/src/errors.rs:514
  variant KeyspacesMetadataError::SchemaKeyspacesInvalidColumnType, previously in file /home/runner/work/scylla-rust-driver/scylla-rust-driver/target/semver-checks/git-9441b0593385e6aef6af482334b3ad81fcb7c047/62fca62783f2893603c618574acc5e36f91a0e69/scylla/src/errors.rs:476

     Summary semver requires new major version: 2 major and 0 minor checks failed
    Finished [  49.307s] scylla
    Building scylla-cql v0.4.0 (current)
       Built [  11.397s] (current)
     Parsing scylla-cql v0.4.0 (current)
      Parsed [   0.033s] (current)
    Building scylla-cql v0.4.0 (baseline)
       Built [  11.198s] (baseline)
     Parsing scylla-cql v0.4.0 (baseline)
      Parsed [   0.035s] (baseline)
    Checking scylla-cql v0.4.0 -> v0.4.0 (no change)
     Checked [   0.129s] 127 checks: 127 pass, 0 skip
     Summary no semver update required
    Finished [  23.519s] scylla-cql
make: *** [Makefile:61: semver-rev] Error 1

[muzarski]

v1.1: addressed comments

[muzarski]

Rebased on main

[muzarski]

v2: applied @Lorak-mmk suggestion. Introduced MetadataFetchError. I managed to edit existing commits.

[muzarski]

Rebased on main

[Lorak-mmk]

I really like the new errors here!