chore(benchmarks): make readme and filenames consistent

[dubloom]

What does this PR do?

• Adds di_ prefix in the benchmarks/README.md
• Changes the profiler benchmarks prefix to be consistent with the README

Motivation:
I'm adding some benchmarks for error_tracking and some information was missing/inconsistent in the benchmarks folder/README

Change log entry
No.

How to test the change?
CI is green

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.75%. Comparing base (01fa6c8) to head (b366786).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #4623   +/-   ##
=======================================
  Coverage   97.75%   97.75%           
=======================================
  Files        1417     1417           
  Lines       86327    86327           
  Branches     4349     4349           
=======================================
  Hits        84388    84388           
  Misses       1939     1939           

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[datadog-datadog-prod-us1]

Datadog Report

Branch report: dubloom/chore/nit-in-benchmarks
Commit report: b366786
Test service: dd-trace-rb

✅ 0 Failed, 21262 Passed, 1373 Skipped, 3m 39.34s Total Time

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-05-05 12:03:18

Comparing candidate commit b366786 in PR branch dubloom/chore/nit-in-benchmarks with baseline commit 01fa6c8 in branch master.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 31 metrics, 2 unstable metrics.