fuzz: refactor fixture processing harnesses to use &mut self

[buffalojoec]

When working with fixtures, it's sometimes necessary to configure Mollusk's program cache before running some set of fixtures.

In the current implementation, functions such as process_and_validate_fixture are associated functions, so they vend their own new Mollusk instance internally and use that for processing the fixture, giving the developer no opportunity to configure the program cache (or any other configurations).

This change makes these functions methods using &mut self, which causes the loaded fixture to update the current Mollusk instance's configurations based on the fixture.

A few notes:

• For any developers who do not wish to alter their Mollusk instance based on loaded fixtures, the load_fixture function will no longer vend a Mollusk instance, but the components themselves, allowing developers to do with the components what they wish.
• The run_checks method on the InstructionResult type has been made public, in case comparing all checks in process_and_validate_fixture (or any other Mollusk method for that matter) is too strict. Now, one could run just a subset of checks on the returned result from, say, process_fixture.

cc @febo

[febo]

Would it make sense to have a variant without any data representing the case where you want to check everything from the resulting accounts? It would be a simpler way to do that (no need to add the bool values) and it might be the common case.

Not so sure about the naming that we could have, but maybe something along the lines:

...
/// Validates all resulting accounts.
ResultingAccounts,
/// Validates specific fields of all resulting accounts.
ResultingAccountsFields {
        /// Whether or not to validate each account's data.
        data: bool,
        /// Whether or not to validate each account's lamports.
        lamports: bool,
        /// Whether or not to validate each account's owner.
        owner: bool,
        /// Whether or not to validate each account's space.
        space: bool,
},
/// Validates specific fields of a subset resulting accounts.
ResultingAccountsSubset {
        /// The addresses on which to apply the validation.
        addresses: Vec<Pubkey>,
        /// Whether or not to validate each account's data.
        data: bool,
        /// Whether or not to validate each account's lamports.
        lamports: bool,
        /// Whether or not to validate each account's owner.
        owner: bool,
        /// Whether or not to validate each account's space.
        space: bool,
},
/// Validates specific fields of resulting accounts _except_ the provided addresses.
ResultingAccountsExcept {
        /// The addresses on which to _not_ apply the validation.
        ignore_addresses: Vec<Pubkey>,
        /// On non-ignored accounts, whether or not to validate each account's
        /// data.
        data: bool,
        /// On non-ignored accounts, whether or not to validate each account's
        /// lamports.
        lamports: bool,
        /// On non-ignored accounts, whether or not to validate each account's
        /// owner.
        owner: bool,
        /// On non-ignored accounts, whether or not to validate each account's
        /// space.
        space: bool,
    },
}

[buffalojoec]

Added helpers for this in my most recent commit. Nice suggestion!

[febo]

Looks great! Left a small suggestion.

[febo]

Run a test with the FixtureCheck and they work fine.