Docs: Replace blockdiag/seqdiag with Mermaid

Docs: Replace blockdiag/seqdiag with Mermaid

Replace the abandoned sphinxcontrib-blockdiag and sphinxcontrib-seqdiag
Sphinx extensions with sphinxcontrib-mermaid in docs configuration.

None of the documentation in this repository uses blockdiag or seqdiag
directives; this is a config-only cleanup.
Updated to use released parent pom 3.3.0 to resolve compile issues due to
expired snapshot.

Issue-ID: CIMAN-33
Change-Id: I26c66e4f0ee578b350e0b246fd193bfc18b147b0
Signed-off-by: Claude <noreply@anthropic.com>
Signed-off-by: Matthew Watkins <mwatkins@linuxfoundation.org>
Signed-off-by: Dan Timoney <dtimoney@att.com>