Fix issue with multiple versions

[nikolai-laevskii]

Description

• Updated installers
• Refactored DotnetCoreInstaller
• Added LTS runtime installation before requested dotnet installation (see Detailed solution description)
• Added E2E tests that check for the problem described in the issue

Detailed solution description

When dotnet is installed after usage of some other version, install script fails to override dotnet.exe as it appears to be used by a process. Workaround is to pass --skip-unversioned-files flag to the install script and avoid overriding this file altogether. However, to ensure better compatibility and to avoid vulnerability issues, LTS runtime is now installed first, providing up-to-date unversioned files (such as CLI) for further usage.

• Additional E2E tests were added to address this issue in the future.
• The new E2E test failing on the main branch with an error as described in issue: https://github.com/nikolai-laevskii/setup-dotnet/actions/runs/4961107288/jobs/8877470722

Failed checks
2 checks failed: it thinks that install scripts are not up-to-date for some reason, might be a problem with cache

Related issue:
actions#387

Check list:

• Mark if documentation changes are required.
• Mark if tests were added or updated to cover the changes.