[Sampler.AWS] AWS X-Ray remote sampler part 1

[srprash]

New feature: AWS X-Ray remote sampler.

I am going to create a series of PRs for adding the X-Ray remote sampling support for OTel via the newOpenTelemetry.Sampler.AWS package.
For more details on the X-Ray remote sampling, please refer to this doc: https://docs.aws.amazon.com/xray/latest/devguide/xray-concepts.html#xray-concepts-sampling

Changes

This PR is the first one in the series and introduces the following:

• A basic builder and concrete class for the AWSXRayRemoteSampler. The builder provides the configuration for the polling interval and the Otel collector xray proxy endpoint.
• The AWSXRayRemoteSampler overrides the ShouldSample method but currently throws an NotImplementedException exception when an activity/span is started.
• The AWSXRayRemoteSampler upon initialization spins up a scheduled thread to fetch sampling rules from the X-Ray service. The sampling rules fetched are not stored anywhere in this current PR, but further implementation will build up on this logic.

For significant contributions please make sure you have completed the following items:

• Appropriate CHANGELOG.md updated for non-trivial changes

[codecov]

Codecov Report

Merging #1091 (e137b5e) into main (8194f05) will increase coverage by 0.12%.
The diff coverage is 78.94%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1091      +/-   ##
==========================================
+ Coverage   71.12%   71.24%   +0.12%     
==========================================
  Files         222      229       +7     
  Lines        8360     8493     +133     
==========================================
+ Hits         5946     6051     +105     
- Misses       2414     2442      +28     

Impacted Files	Coverage Δ
...OpenTelemetry.Sampler.AWS/AWSSamplerEventSource.cs	23.07% <23.07%> (ø)
.../OpenTelemetry.Sampler.AWS/AWSXRayRemoteSampler.cs	61.90% <61.90%> (ø)
.../OpenTelemetry.Sampler.AWS/AWSXRaySamplerClient.cs	88.09% <88.09%> (ø)
src/OpenTelemetry.Sampler.AWS/SamplingRule.cs	89.74% <89.74%> (ø)
...lemetry.Sampler.AWS/AWSXRayRemoteSamplerBuilder.cs	92.30% <92.30%> (ø)
...nTelemetry.Sampler.AWS/GetSamplingRulesResponse.cs	100.00% <100.00%> (ø)
...rc/OpenTelemetry.Sampler.AWS/SamplingRuleRecord.cs	100.00% <100.00%> (ø)

[Kielek]

One last thing before approval for the scaffolding, please add projects to https://github.com/open-telemetry/opentelemetry-dotnet-contrib/blob/595a9a34e3e0f10f25df64153a83889ad386a3fc/.github/component_owners.yml (in alphabetical order).

[srprash]

@Kielek There's some failure in the sanitycheck/misspell workflow which I believe is unrelated to these changes. Can you take a look into it? Thanks!

[Kielek]

@srprash rerun passed. Probably network related issue

[Kielek]

LGTM , as a scaffolding for further work

[srprash]

@Kielek So is it good to be merged? I will build upon this in future PRs.

[Kielek]

@utpilla , could you please check?

[utpilla]

Approved with some suggestions on fixing content of README and using $(RepoRoot).