[Otlp] Make sure Otlp trace and metric exporters have dedicated options instances

[CodeBlanch]

Relates to #4043
Relates to #4058

Changes

• This is a little deeper fix than what I did on [OtlpExporter] Registration extension configuration delegate fix #4058. Previously we still modified a single instance. For things like endpoint which are being set each time it isn't a problem. But considering a property like PersistentBlobProvider being added on [metrics branch] Add configuration of persistent storage to OTLP Exporter #4121 if it is set for traces, metrics would inherit it unless it was cleared or set to something else. We could run into hard to detect and subtle bugs. To make it work nicely without needing some mechanism to "reset" options back to default, I decided to just make sure we new up a new instance when building the processor/exporter. The best fix would be to have dedicated classes (eg OtlpTraceExporterOptions & OtlpMetricExporterOptions) but hard to do without breaking things. @alanwest had the idea to introduce those and clean this up when we split up the projects.

Example which works fine without this change:

.WithTraces({
  endpoint = traceEndpoint
})
.WithMetrics({
  endpoint = metricEndpoint
})

Example which will be bugged without this change:

.WithTraces({
  endpoint = traceEndpoint
})
.WithMetrics({
  headers = metricHeaders
})

That second example depending on whether TracerProvider or MeterProvider is started first, either trace will have metricHeaders or metrics will have traceEndpoint.

[codecov]

Codecov Report

Merging #4200 (7d271bf) into main (d0829ff) will increase coverage by 0.01%.
The diff coverage is 100.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4200      +/-   ##
==========================================
+ Coverage   85.51%   85.53%   +0.01%     
==========================================
  Files         291      291              
  Lines       11380    11398      +18     
==========================================
+ Hits         9732     9749      +17     
- Misses       1648     1649       +1     

Impacted Files	Coverage Δ
...nTelemetryProtocol/OtlpMetricExporterExtensions.cs	96.96% <100.00%> (+0.47%)	⬆️
...metryProtocol/OtlpTraceExporterHelperExtensions.cs	96.66% <100.00%> (+0.58%)	⬆️
...ter.ZPages/Implementation/ZPagesActivityTracker.cs	97.14% <0.00%> (-2.86%)	⬇️

[alanwest]

good catch