Playwright parallelization

[bznein]

This PR aims at reducing the total runtime of playwright tests by performing the following:

• Separate Chromium and Webkit projects into different tests execution, effectively halving the runtime (biggest improvement)
• Build the frontend once and reuse it in all tests
• Only install the necessary browser for each test
• Cache NPM dependencies

There is also a separate commit that fixes some logic for handling retries in regtest tests. It is not strictly needed but it doesn't hurt. Open to moving it to a different PR if anyone fells strongly about it :D

Before asking for reviews, here is a check list of the most common things you might need to consider:

• updating the Changelog
• writing unit tests
• checking if your changes affect other coins or tokens in unintended ways
• testing on multiple environments (Qt, Android, ...)
• having an AI review your changes

[Beerosagos]

CI and playwright aren't exactly my area of expertise, but the changes look good to me and Codex 😬