Refactor Index, remove unused indirections

[trieloff]

This simplifies index a bit

• refactor(index): remove no-op optedIn function
• chore(index): supress log messages when weight is not 1
• refactor(index): remove feature flag for reportAllChanges
• refactor(web-vitals): pin web vitals version to guard against breaking changes
• test(web-vitals): test that web-vitals does not conflict with pre-existing script
• test(index): exclude untestable code from coverage
• refactor(index): remove list of default tracking events, it is redundant