Only public APIs need SUPPORT_COROSYNC notes

In T788#12132, @nrwahl2 wrote:

For 3.0.0 (T793)... For pcmk_cluster_t, we can replace all deprecated struct members except destroy() and cpg with a void *private member that can be used internally for a new internal struct containing the deprecated members.

Why can't destroy and cpg become part of the void *private member at 3.0.0? It seems that's the point of creating the setter functions for those, so that external users no longer need direct access.

I suspect the use case for this feature was being able to set an explicit value in one block of meta-attributes, then have another rule-based block of attributes that resets the value to the default. Simply omitting the meta-attribute from the rule-based block wouldn't cause the explicit value to be removed.

In T817#12112, @nrwahl2 wrote:

From the GitHub discussion:

I believe it was originally for testing the code paths. Not needed anymore

Optionally, we could have a (possibly hidden) --async-call option for developer use, that starts a mainloop and runs a callback function that processes the reply.