Add OpenTracing section to the compliance matrix.

[carlosalberto]

As we are looking to stabilize the OpenTracing compatibility section, we want to keep track of the actual features in different SIGs.

[github-actions]

This PR was marked stale due to lack of activity. It will be closed in 7 days.

[SergeyKanzhelev]

@carlosalberto I've reassigned to you to move this forward as per e-mail from @bhs.

[carlosalberto]

@yurishkuro Updated, please review - I'm keeping the Baggage support among execution units for now, while we decide whether we discard support for this or not.

[bhs]

ping @carlosalberto on this (and @yurishkuro's comments)... this PR is on the critical path to formally archiving the OpenTracing project within CNCF so would be good to keep it moving, though obviously not P0 or anything. :)

[carlosalberto]

@yurishkuro Applied feedback. The only remaining bit is the one regarding custom propagators - which is useful in case users want to use a different propagator for OpenTracing's HTTP_HEADERS and TEXT_MAP (by default we use the global OTel propagators for both types).

[carlosalberto]

@yurishkuro Please review. Removed some parts (such as the Create Tracer with custom propagators) as they are already included in features that MUST be supported in their respective sections.

Left the error mapping one without a link as it is mentioned in both sections. It can probably be also removed though, although I'd personally keep that one in order to signal implementers of its importance ;)

[tedsuo]

Thanks for picking this up Carlos.