[ENG-3325] chore: refactor workflows

[teebszet]

🔘 PR Type

• CI related changes

📜 Background

https://www.notion.so/xverseapp/Xverse-Web-Extension-Release-Instructions-f850e51a4a9f4eba94b9ad27eb8beca6

automating steps 6-8

https://linear.app/xverseapp/issue/ENG-3325

🔄 Changes

• required some refactoring of the workflows
  • refactor build.yaml to:
    • trigger only for PRs not named like a release PR
  • create a build-rc.yaml for release PRs to:
    • trigger on pull_request events to main & develop named like a release PR
    • create the release (moved from create-release-pr.yml)
    • build and upload the release asset (moved from release.yml)
  • refactor release.yaml to:
    • trigger on merge of release PR to main
    • look for the latest release candidate and create the 'latest' release with the same target_comittish

[github-actions]

Test with build here: https://github.com/secretkeylabs/xverse-web-extension/actions/runs/7243430731

[dhriaznov]

LGTM 👍