Reduce allocations in telemetry

[martintmk]

Details on the issue fix or feature implementation

Closes #1312

Confirm the following

• I started this PR by branching from the head of the default branch
• I have targeted the PR to merge into the default branch
• I have included unit tests for the issue/feature
• I have successfully run a local build

[codecov]

Codecov Report

Merging #1321 (56880f5) into main (ce97ea5) will increase coverage by 0.11%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1321      +/-   ##
==========================================
+ Coverage   83.37%   83.49%   +0.11%     
==========================================
  Files         268      269       +1     
  Lines        6335     6379      +44     
  Branches     1001     1004       +3     
==========================================
+ Hits         5282     5326      +44     
  Misses        844      844              
  Partials      209      209              

Flag	Coverage Δ
linux	?
macos	83.49% <100.00%> (+0.11%)	⬆️
windows	83.49% <100.00%> (+0.11%)	⬆️

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Impacted Files	Coverage Δ
src/Polly.Extensions/Telemetry/EnrichmentUtil.cs	100.00% <ø> (ø)
...olly.Core/Telemetry/ResilienceStrategyTelemetry.cs	100.00% <100.00%> (ø)
...lly.Core/Telemetry/TelemetryEventArguments.Pool.cs	100.00% <100.00%> (ø)
...rc/Polly.Core/Telemetry/TelemetryEventArguments.cs	100.00% <100.00%> (ø)
src/Polly.Core/Utils/ObjectPool.cs	100.00% <100.00%> (ø)
...lly.Extensions/Telemetry/EnrichmentContext.Pool.cs	100.00% <100.00%> (ø)
...rc/Polly.Extensions/Telemetry/EnrichmentContext.cs	100.00% <100.00%> (ø)
...s/Telemetry/ResilienceTelemetryDiagnosticSource.cs	100.00% <100.00%> (ø)
...xtensions/Telemetry/TelemetryResilienceStrategy.cs	100.00% <100.00%> (ø)

... and 3 files with indirect coverage changes