Support in-place upgrades and support non-curl systems

[lsegal]

Since wget is supported in the install script, do not rely on curl to download the script. Instead download via ureq.

[qltysh]

The code coverage on the diff in this pull request is 0.0%

Drilldown

Path	File Coverage Δ
qlty-check/src/tool/command_builder.rs	2.6
qlty-cli/src/initializer/scanner/gemfile.rs	-0.3
qlty-check/src/tool/ruby/sys/macos.rs	3.1
qlty-check/src/tool/download.rs	0.7
qlty-check/src/tool/ruby/sys/linux.rs	-1.6

[lsegal]

Just manually tested on Windows / Linux / macOS both in and outside of ~/.qlty and they all work.