Add parser for publisher v4 prefix list

[zenparsing]

Resolves brave/brave-browser#10056

Submitter Checklist:

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
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  • 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-issues-with-tracking-protection
  • https://github.com/brave/brave-browser/wiki/QA-Guide

Test Plan:

Reviewer Checklist:

• New files have MPL-2.0 license header.
• Request a security/privacy review as needed.
• Adequate test coverage exists to prevent regressions
• Verify test plan is specified in PR before merging to source

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.

[emerick]

LGTM, a couple of comments.

[bridiver]

there is already existing code for handling Brotli in chromium BrotliSourceStream

[bridiver]

in fact most of this code appears to be copied from chromium and there's no reason to do that. We can just use it directly

[zenparsing]

For future reference, reusing BrotliSourceStream from net/filter would require creating a SourceStream class from a string (example here).

[zenparsing]

This approach of compressing the data inside of the protobuf message is inspired by Safe Browsing (see here), which embeds Rice-encoded prefix delta values into the message when the prefix lengths are 4 bytes. This message format will give us the option of moving in that direction in the future if we choose.