Handle debug flags sent from C-S-S

[muodov]

Reviewer: @shakyShane
CC: @jonathanKingston
Depends on: duckduckgo/content-scope-scripts#648

Description:

MVP infra for generic debug flags for C-S-S features. This is not yet a full Messaging implementation, which should come in later stages of the project.

Steps to test this PR:

0. Add a log to the breakage report, or set up a proxy to see the breakage pixel URL
1. Build the extension with C-S-S changes from Breakage debug flags content-scope-scripts#648
2. Open any page with enabled protections (e.g. example.com)
3. Trigger the protections:

• navigator.hardwareConcurrency
• (await navigator.getBattery()).charging (Chromium only)

4. Send a breakage report form
5. Verify that debugFlags parameter is present in the pixel URL

Automated tests:

• Unit tests
• Integration tests

Reviewer Checklist:

• Ensure the PR solves the problem
• Review every line of code
• Ensure the PR does no harm by testing the changes thoroughly
• Get help if you're uncomfortable with any of the above!
• Determine if there are any quick wins that improve the implementation

PR Author Checklist:

• Get advice or leverage existing code
• Agree on technical approach with reviewer (if the changes are nuanced)
• Ensure that there is a testing strategy (and documented non-automated tests)
• Ensure there is a documented monitoring strategy (if necessary)
• Consider systems implications

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