[9.20] chg: dev: Use atomics for CMM_{LOAD,STORE}_SHARED with ThreadSanitizer

[9.20] chg: dev: Use atomics for CMM_{LOAD,STORE}_SHARED with ThreadSanitizer

Upstream has removed the atomics implementation of CMM_LOAD_SHARED and
CMM_STORE_SHARED as these can be used also with non-stdatomics types.
As we only use the CMM api with stdatomics types, we can restore the
previous behaviour to prevent ThreadSanitizer warnings.

Closes #5660

Backport of MR !11288

Merge branch 'backport-5660-use-atomics-for-CMM-api-with-thread-sanitizer-9.20' into 'bind-9.20'

See merge request isc-projects/bind9!11290