APM SDK Terminology

[brett0000FF]

What does this PR do?

• Updates single-sourced public documentation to replace "tracer" and "tracing library" with "APM SDK".

Motivation:

DataDog/documentation#24255

Additional Notes:

Please don't merge into release until the documentation PR linked above is merged.

How to test the change?

Unsure? Have a question? Request a review!

[ivoanjo]

I guess:

• https://github.com/DataDog/dd-trace-rb/blob/master/README.md
• https://github.com/DataDog/dd-trace-rb/blob/master/datadog.gemspec#L21
• the repo description
  

should also be updated to reflect this once it's ready to go?

[pr-commenter]

Benchmarks

Benchmark execution time: 2024-07-31 16:03:12

Comparing candidate commit 1705fec in PR branch brett0000FF/dd-sdks with baseline commit 47f12db in branch master.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 10 metrics, 2 unstable metrics.

[aliciascott]

this looks good, I'll let you merge once the related PR is reviewed (editorial review)

[brett0000FF]

should also be updated to reflect this once it's ready to go?

@ivoanjo - Yeah, I talked about this with @tushar-datadog . I think for consistency's sake, we should keep the terminology consistent wherever possible.