Add tracePropagationTargets option

[smeubank]

Problem Statement

There is no mechanism to control where tracing is or is not propagated to. Leading to possibly sending useless tracing headers and contextual data to endpoints where it is not relevant.

this is from the PHP issue https://github.com/getsentry/sentry-php/issues/1361 but not sure what GuzzleTracingMiddleware

The GuzzleTracingMiddleware currently propagates the sentry-trace and soon the baggage header on each instrumented request.

Solution Brainstorm

Add the tracePropagationTargets option.

https://develop.sentry.dev/sdk/performance/#tracepropagationtargets

this is from the PHP issue https://github.com/getsentry/sentry-php/issues/1361 but not sure what GuzzleTracingMiddleware

The GuzzleTracingMiddleware currently propagates the sentry-trace and soon the baggage header on each instrumented request.