feat: implement isCompressionEligable method

[astorm]

Implements: #2604

This PR finishes up the span compression work by implementing an isCompressionEligible method that uses propagated trace context headers, exit span, and outcome to determine whether a span is eligible for compression. It also ties up a few other loose ends that came up while implementing it.

• Span compression is enabled by default
• HTTP 2 requests will now propagate the the trace context headers
• Span compression disabled for tedious and cassandra tests (per other "db exit spans")
• Timing adjusted for "same kind compression" test as a possible fix for observed flakiness

Checklist

• Implement code
• Add tests
• [ ] Update TypeScript typings
• Update documentation
• Add CHANGELOG.asciidoc entry
• Commit message follows commit guidelines

[apmmachine]

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• Start Time: 2022-04-26T20:38:51.271+0000

• Duration: 20 min 4 sec

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Total	247303

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[trentm]

Implements: #2604

If you use Closes, Fixes, or Resolves then GitHub will automatically link this PR to the issue. Unless you intentionally don't want that?

• HTTP 2 requests will now propagate the the trace context headers

Nice. This is: #1830

• Span compression is enabled by default

This section of "configuration.asciidoc" should be updated for it being on by default now:

[[span-compression-enabled]]
==== `spanCompressionEnabled`

...