**Is your feature request related to a problem? Please describe.** Both ios and android defines samping ratiofunctionality. It is not documented in gdi-spec. **Describe the solution you'd like** Common way to define span filtering for: - `enableSessionBasedSampling(double)` https://docs.splunk.com/observability/en/gdi/get-data-in/rum/android/configure-rum-android-instrumentation.html - `sessionSamplingRatio` https://docs.splunk.com/observability/en/gdi/get-data-in/rum/ios/configure-rum-ios-instrumentation.html#general-settings - **Describe alternatives you've considered** N/A **Additional context** Review for https://github.com/signalfx/gdi-specification/issues/255