We did not have an external capability to tear down one ring; we had to
tear down all rings. A way to selectively tear down one ring will be a
quality of life improvement.

Add a method under RMMRings that tears down one ring.
The external API to invoke this is not implemented in this commit.

On naming: treated tearDown as 2 words because the API uses "tearDownAllRings".
I valued consistency on the API over consistenty in the internal implementation.

confusion when writing this code, this is not a de-duplication,
this is out of range error

this enables checking and ignoring teardown request if one is already in
progress

Dahyeon still does not understand what this function does, but after
consultation with Douglas A we've identified that this function should
not be in tearDown functions (for both One and All variant) and should
go somewhere else.

It looked like the function was mis-translated from Python slow control
in a wrong place.

since we are using try_lock and pass-through if lock is already engaged,
there is little risk of TOCTTOU. Since thie state collection is not a
mutating operation it can be safely outside of lock.

If for some reason status_register cannot be obtained due to an error
inside, it will result in the lock operation not happening (since nobody
is catching the error here)

this way, it is possible to both use try_lock
  (-> enables pass-through if lock is already engaged)
while automatically unlocking when the lock object is destructed

https://en.cppreference.com/w/cpp/thread/unique_lock

no need to have two functions that do the same things with slightly
different interface.

BREAKING CHANGE: external interface not affected. this change alters
RMMRings interface.

the existing interface (void) has not been changed yet, which will be
done later.

consequenctly, some underlying functions also changed their return type
from void to RMMResult or rmmStatus depending on surrounding code

refactor tearDownRing to be used standalone

See merge request !40

Refactor tearDownRing API to return rmmStatus intead of void

See merge request !41

this function brings up all rings, but in sequence instead of one by
one. intended for developer use. User interface and external API changes
are not added in this commit

add bringUpAllRingsInSequence

Closes ICSHWI-20691

See merge request !42