[canary] 🚀 Use dataclasses for 3way merging

[cdesouza-chromium]

This PR introduces several data classes to better compartimentalise the data being used in this tool. The previous code relied on a very large method to do all the operations necessary during patch resolution.

The management of the continuation file is also being overhauled to be its own code, separate from PatchFailureResolver, as the continuation file also stores things like working_version which is not necessarily part of the merge process.

Version Type
This type is being introduced to simplify the operations around version in Brockit. The code is now easier to understand, and the operations are grouped.

Infra Mode
This new execution mode suppresses the status page, and as a replacement, provides terminal "keep alive" output, to allow the CI to be kept alive.

A separate issue has been created to come up with something better than pickle for serialisation brave/brave-browser#44726

Resolves brave/brave-browser#44690
Resolves brave/brave-browser#44727

Submitter Checklist:

• I confirm that no security/privacy review is needed and no other type of reviews are needed, or that I have requested them
• There is a ticket for my issue
• Used Github auto-closing keywords in the PR description above
• Wrote a good PR/commit description
• Squashed any review feedback or "fixup" commits before merge, so that history is a record of what happened in the repo, not your PR
• Added appropriate labels (QA/Yes or QA/No; release-notes/include or release-notes/exclude; OS/...) to the associated issue
• Checked the PR locally:
  • npm run test -- brave_browser_tests, npm run test -- brave_unit_tests wiki
  • npm run presubmit wiki, npm run gn_check, npm run tslint
• Ran git rebase master (if needed)

Reviewer Checklist:

• A security review is not needed, or a link to one is included in the PR description
• New files have MPL-2.0 license header
• Adequate test coverage exists to prevent regressions
• Major classes, functions and non-trivial code blocks are well-commented
• Changes in component dependencies are properly reflected in gn
• Code follows the style guide
• Test plan is specified in PR before merging

After-merge Checklist:

• The associated issue milestone is set to the smallest version that the
  changes has landed on
• All relevant documentation has been updated, for instance:
  • https://github.com/brave/brave-browser/wiki/Deviations-from-Chromium-(features-we-disable-or-remove)
  • https://github.com/brave/brave-browser/wiki/Proxy-redirected-URLs
  • https://github.com/brave/brave-browser/wiki/Fingerprinting-Protections
  • https://github.com/brave/brave-browser/wiki/Brave%E2%80%99s-Use-of-Referral-Codes
  • https://github.com/brave/brave-browser/wiki/Web-Compatibility-Exceptions-in-Brave
  • https://github.com/brave/brave-browser/wiki/QA-Guide
  • https://github.com/brave/brave-browser/wiki/P3A

Test Plan:

[brave-builds]

Released in v1.78.51