Implement telemetry log

[TonyCTHsu]

What does this PR do?

This PR enables developer to send telemetry logs for internal observability.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 94.39252% with 6 lines in your changes missing coverage. Please review.

Project coverage is 97.86%. Comparing base (d2498fb) to head (5f65370).
Report is 24 commits behind head on master.

Files	Patch %	Lines
spec/datadog/core/telemetry/component_spec.rb	77.77%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3850      +/-   ##
==========================================
+ Coverage   97.83%   97.86%   +0.03%     
==========================================
  Files        1264     1271       +7     
  Lines       75725    75975     +250     
  Branches     3729     3739      +10     
==========================================
+ Hits        74084    74353     +269     
+ Misses       1641     1622      -19     

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[pr-commenter]

Benchmarks

Benchmark execution time: 2024-08-21 10:52:26

Comparing candidate commit 5f65370 in PR branch tonycthsu/telemetry_log with baseline commit b7b99b2 in branch master.

Found 3 performance improvements and 0 performance regressions! Performance is the same for 20 metrics, 2 unstable metrics.

scenario:profiler - Allocations (baseline)

• 🟩 throughput [+124772.281op/s; +139418.282op/s] or [+2.394%; +2.675%]

scenario:profiler - Allocations (profiling disabled)

• 🟩 throughput [+196926.064op/s; +204312.166op/s] or [+3.974%; +4.123%]

scenario:profiler - Allocations (profiling enabled)

• 🟩 throughput [+198401.928op/s; +209347.150op/s] or [+4.046%; +4.270%]

[p-datadog]

I find "sending" to be misleading because nothing is actually sent. Suggest either "attempting to send" or "requested to send" or similar. Also, I would put the message at the end so that it's clear where the diagnostics of this component ends and where the forwarded message is. E.g. "Requested to send telemetry log when telemetry component is not ready: #{message}". Is it possible for telemetry to be never turned on, i.e. it would actually not ever become ready?

[marcotc]

The telemetry object is always created, even if telemetry is disabled

dd-trace-rb/lib/datadog/core/telemetry/component.rb

Lines 45 to 47 in b7b99b2

	Telemetry::Component.new(
	http_transport: transport,
	enabled: enabled,

so it will eventually become no-nil.

I also like that this message is at debug level, so people have to manually enable debug-level logs to see it.

I do agree that the messaging can be more precise.

[ivoanjo]

Minor: Should we perhaps print the whole event and not just the message when logging

[TonyCTHsu]

I don't think printing the whole event is necessary, since the issue is not caused by event itself.

[ivoanjo]

My thinking for this suggestion is, if later we add more information to the event (e.g. stack), we'll need to remember to tweak the debug message, whereas if we print the whole event, then we won't need to touch it again.

[marcotc]

Looks good!
I believe @y9v's and @p-datadog's comments are relevant and should be responded to or addressed.