internal/traceprof/traceproftest: fix flaxy endpoints/hotspots test (D…

…ataDog#1145)

* internal/traceprof/traceprof: fix flaxy endpoints/hotspots test

TestEndpointsAndCodeHotspots fails occasionally in CI. Change the retry
logic so that every required label is checked for in testCommon before
ending the retry loop.

* internal/traceprof/traceproftest: identify reason for test failure

If TestEndpointsAndCodeHotspots fails after too many attempts, show
which condition wasn't met after all the attempts.

internal/version/version.go: bump the lib version to v1.36.0-rc.2

internal/version/version.go: bump the lib version to v1.36.0-rc.1

ddtrace/tracer: only drop P0s when client-side stats are enabled

Currently, if the agent reports that it supports dropping P0s, the trace
agent will begin dropping them, independently of enabling client-side stats
computing. This results in default deployments dropping P0 spans and not
calculating stats on them, meaning trace metrics are wrong.

This only allows dropping P0s if client-side stats computation is enabled.

tracer: profiler endpoints for spans without type (DataDog#1115)

tracer: profiler endpoints for span's without type

inc version

tracer: startup message for hotspots/endpoints

inc version

Update internal version

revert: StartSpanFromContext for Tracer interface (DataDog#1103)

Remove StartSpanFromContext method from ddtrace.Tracer interface to
avoid breaking users that implement this interface.

Revert tracer.StartSpanFromContext to its old behavior of inherting the
span contained in the passed context. This makes sure that users who
write tests that rely on the default NoopTracer see the same behavior as
previously.

This reverts commits 5f95c9f and
6661a9d.