perf(sdk-trace-base): avoid Object.entries in Span.setAttributes

[daniellockyer]

Which problem is this PR solving?

Whilst looking at the performance overhead of OTel, I noticed setAttributes in unusually heavy in comparison to setAttribute. Turns out, we're using Object.entries for the loop here, which is much heavier than a standard for-in loop. This change has been made several other times in this repo, such as in #5866 and #6287.

Part of the flamegraph showing the setAttributes call has overhead in comparison to setAttribute:

Many instrumentations use setAttributes, including http, so we should see strong improvements across the board.

Before:

create spans (10 attributes) x 1,040,461 ops/sec ±1.81% (97 runs sampled)
create spans (10 attributes w/ setAttributes) x 842,071 ops/sec ±1.78% (94 runs sampled)

After:

create spans (10 attributes) x 1,013,509 ops/sec ±1.60% (96 runs sampled)
create spans (10 attributes w/ setAttributes) x 1,025,856 ops/sec ±1.42% (99 runs sampled)

You can see span creation with setAttributes is now on par with the performance of the benchmark using 10x setAttribute thanks to the 22% performance improvement 🚀

refs #6100

Short description of the changes

Replace Object.entries with a for-in loop for better performance.

Also adds a benchmark test for span creation using setAttributes.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Tests still pass, and see benchmark results from above.

Checklist:

• Followed the style guidelines of this project
• Unit tests have been added
• Documentation has been updated

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: daniellockyer / name: Daniel Lockyer (81f8a82, bc959dd)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.75%. Comparing base (2f73776) to head (81f8a82).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6514   +/-   ##
=======================================
  Coverage   95.75%   95.75%           
=======================================
  Files         364      364           
  Lines       12095    12096    +1     
  Branches     2884     2885    +1     
=======================================
+ Hits        11581    11582    +1     
  Misses        514      514           

Files with missing lines	Coverage Δ
packages/opentelemetry-sdk-trace-base/src/Span.ts	99.12% <100.00%> (+<0.01%)	⬆️

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