tracer: improve debug message for propagating tag length limit reached

[katiehockman]

What does this PR do?

Adds additional context to the debug message that is sent if the propagating tag exceeds the maximum configured length.

Motivation

This should make it easier for customers to decide how much they need to increase DD_TRACE_X_DATADOG_TAGS_MAX_LENGTH.

Reviewer's Checklist

• Changed code has unit tests for its functionality at or near 100% coverage.
• System-Tests covering this feature have been added and enabled with the va.b.c-dev version tag.
• There is a benchmark for any new code, or changes to existing code.
• If this interacts with the agent in a new way, a system test has been added.
• Add an appropriate team label so this PR gets put in the right place for the release notes.

For Datadog employees:

• If this PR touches code that handles credentials of any kind, such as Datadog API keys, I've requested a review from @DataDog/security-design-and-guidance.
• This PR doesn't touch any of that.

Unsure? Have a question? Request a review!

[pr-commenter]

Benchmarks

Benchmark execution time: 2023-11-30 17:06:06

Comparing candidate commit 1608ebc in PR branch katie.hockman/improve-debug-message with baseline commit 2a84dea in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 39 metrics, 2 unstable metrics.