Update branch dashing to support Dashing only

[asorbini]

This PR updates branch dashing to make it buildable only with the Dashing release.

The PR removes all "feature flags" from static_config.hpp, including RMW_CONNEXT_RELEASE and any code meant to support later releases.

The code was changed assuming the following "feature configuration":

Feature	Value
RMW_CONNEXT_RELEASE	RMW_CONNEXT_RELEASE_DASHING
RMW_CONNEXT_HAVE_PKG_RMW_DDS_COMMON	0
RMW_CONNEXT_HAVE_SCOPE_EXIT	0
RMW_CONNEXT_HAVE_GET_DOMAIN	0
RMW_CONNEXT_HAVE_OPTIONS	0
RMW_CONNEXT_HAVE_OPTIONS_PUBSUB	0
RMW_CONNEXT_HAVE_INCOMPATIBLE_QOS	0
RMW_CONNEXT_HAVE_INCOMPATIBLE_QOS_EVENT	0
RMW_CONNEXT_HAVE_LIFESPAN_QOS	0
RMW_CONNEXT_HAVE_MESSAGE_LOST	0
RMW_CONNEXT_HAVE_SERVICE_INFO	0
RMW_CONNEXT_HAVE_LOCALHOST_ONLY	0
RMW_CONNEXT_HAVE_TAKE_SEQ	0
RMW_CONNEXT_HAVE_SECURITY	0
RMW_CONNEXT_HAVE_COMMON_MUTEX	0
RMW_CONNEXT_HAVE_LOAN_MESSAGE	0
RMW_CONNEXT_HAVE_MESSAGE_INFO_TS	0
RMW_CONNEXT_HAVE_GET_INFO_BY_TOPIC	0
RMW_CONNEXT_HAVE_QOS_PROFILE_API	0
RMW_CONNEXT_HAVE_TIME_UTILS	0

Note to reviewers: It would be great to review these changes but they are somewhat trivial. I'm creating this PR mainly to keep track of them for future reference.

[asorbini]

CI jobs to validate the changes (note: first time running unit tests for Dashing 🤞🏼):

• ci_linux:
  • 
  • 
  • (failed because rmw_connext_cpp was excluded, but rmw_connextdds built successfully)
  • (up to rmw_connextdds only)

[asorbini]

Backported rmw_dds_common from 79af623