[draft] HTTP user-agent and URL filtering

[SylvainJuge]

Relates to #826

This is a draft implementation:

• reusing rule based sampler implementation from contrib
• using ELASTIC_OTEL_EXPERIMENTAL_HTTP_IGNORE_URLS config option to ignore URLs (regex)
• using ELASTIC_OTEL_EXPERIMENTAL_HTTP_IGNORE_USER_AGENTS config option to ignore user-agents (regex)
• runtime configuration not implemented yet

Next Steps

• switch implementation to use "composable rule based sampler" that is/should be included in the SDK.
• settle on configuration options names
• settle on configuration options syntax (regex or wildcards ?)
  • update: using wildcards as it's what is being used in composable rule based sampler + part of the configuration recommendations.
• add support for runtime configuration
• add end-to-end test, maybe also covering the runtime configuration

[SylvainJuge]

one of the next steps would be to switch to "composable rule based sampler" as it should now be available and would help switch to wildcards.