perf(sdk-metrics): optionally capture active context for sync instruments

[legendecas]

Which problem is this PR solving?

When no AttributesProcessor are registered, the context argument is not used.
This makes the context.active() optional unless there is an AttributesProcessor registered.

No impact on public APIs.

main:
Counter.add (fixed attributes) x 25,533,509 ops/sec ±0.81% (95 runs sampled)
Counter.add (varied attributes, 100 combos) x 24,512,358 ops/sec ±0.55% (98 runs sampled)

PR:
Counter.add (fixed attributes) x 30,876,145 ops/sec ±1.18% (91 runs sampled)
Counter.add (varied attributes, 100 combos) x 31,385,201 ops/sec ±0.83% (96 runs sampled)

+21%/+28%

Follow-up: replace noop AttributesProcessor with undefined to identify Views with no AttributesProcessor configured.

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

• New test on passing context to attribute processors.

Checklist:

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

Refs: #6100

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.58%. Comparing base (dddbc0e) to head (d5c460f).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6848   +/-   ##
=======================================
  Coverage   95.58%   95.58%           
=======================================
  Files         388      388           
  Lines       13152    13163   +11     
  Branches     3001     3004    +3     
=======================================
+ Hits        12571    12582   +11     
  Misses        581      581           

Files with missing lines	Coverage Δ
packages/sdk-metrics/src/Instruments.ts	96.07% <100.00%> (ø)
...ckages/sdk-metrics/src/state/AsyncMetricStorage.ts	100.00% <100.00%> (ø)
...ages/sdk-metrics/src/state/DeltaMetricProcessor.ts	100.00% <100.00%> (ø)
packages/sdk-metrics/src/state/MeterSharedState.ts	98.33% <ø> (-0.03%)	⬇️
...dk-metrics/src/state/MultiWritableMetricStorage.ts	100.00% <100.00%> (ø)
...ackages/sdk-metrics/src/state/SyncMetricStorage.ts	100.00% <100.00%> (ø)

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