aemfvp-a-rme: update documentation for 2023.12.22 release

Update documentation about the changes being introduced in the
2023.12.22 release of the Base AEM-A-RME FVP platform software
stack. Updates include -

- updated basic information around CCA.
- moved setup workspace, build and docker setup in new guides.
- added use case for parallel realm and nsvm boot.
- added use case for SSH connection test between guest and realm.
- elaborated usecases with pre-requisites, steps and expected outcome.

Signed-off-by: Nitin Sharma <nitin.sharma3@arm.com>
Change-Id: Ic5d047c26145bfd419854c3a91c861f80f27ad15