Fix adblock default ruleset reparsing on startup

[atuchin-m]

Resolves brave/brave-browser#33718
Resolves brave/brave-browser#33532

The root of the issue is AdBlockFiltersProviderManager singleton. It subscribes to all the providers (in AdBlockFiltersProviderManager::AddProvider) => it gets notifications about an update in every provider.

Also, AdBlockFiltersProviderManager implements both AdBlockFiltersProvider and AdBlockFiltersProvider::Observer interfaces, acting like a decorator and proxying all the OnChanged to the listeners. The listeners are instances of SourceProviderObserver for the both engines (the manager is passed as AdBlockFiltersProvider* here
As a result, both engine observers get notifications about all the updates and rebuild the combined list of every update.

The PR fixes it in safe and straightforward way: adding to Observer::OnChange() extra information about what kind of source was updated. This allows us to filter out unnecessary notifications.

The PR:

• implement a logic to suppress rebuilding the default engine on notifications about additional engine updates;
• adds extra traces and UMA to track the number of engine rebuilding;
• adds a browser test to verify the number of updates.

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 lint, 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/Custom-Headers
  • 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:

1. Verify that adblock engine works correctly (QA team);
2. Verify the startup performance (perf team).

[atuchin-m]

That will prevent us from ocasionally calling deserializing from UI thread.

[bridiver]

the OnDATLoaded method was actually removed in @antonok-edm's PR. I don't think we load dat files anymore

[atuchin-m]

To clarify the expectations in format: {default engine updates, additional engine updates} in the begin of the test => the same of the end of the test

1. (before the PR) {1, 1} => {3, 3}
2. (after the PR) {1, 1} => {2, 2}
3. (what we actually want in a long term perspective) {0, 0} => {1, 1}

UPD: changed the comment to match the latest changes.

[bridiver]

I think this looks ok, but I'd wait on @antonok-edm to merge

[kjozwiak]

Verification PASSED on Win 11 x64 using the following build(s):

Brave | 1.61.45 Chromium: 118.0.5993.96 (Official Build) nightly (64-bit)
-- | --
Revision | 31c36588a37ea88c2276d901ebd20dbf2344fde3
OS | Windows 11 Version 22H2 (Build 22621.2428)

Basically ensured that adblocking as working when running through #20137 (comment). QA will also run through some spot checks when we run through manual passes via 1.59.x.