Improvements to GitHub CI

[andrei-polukhin]

Several minor improvements to the GitHub CI workflow:

• more descriptive name (there is no automatic version increment);
• workflow is invoked on pull_request (on push may be too late if a non-compiling PR is merged);
• allowing support for different Go version (the case is the release of 1.22 - the go.mod specifies 1.21, but the +1 minor version is supported according to the official Go standard, so we support both versions);
• dropping the mention of the integrationtest directory (find . -name 'integrationtest' in root gives nothing).

[andrei-polukhin]

@YaroslavPodorvanov, please review. I also like to contribute to new codebases, so I'd appreciate being given contributor rights to the repository. Thanks.

[YaroslavPodorvanov]

Current CI is fine