* Remove API 720 guards for tenants (experimental feature) and the cluster ID special keys (no need to guard)
* Enable the relaxed special key access in transactions that need to use special key-space APIs introduced in 7.2
* flow: add ApiVersion to replace hard coding api version
Instead of hard coding api value, let's rely on feature versions akin to
ProtocolVersion.
* ApiVersion: remove use of -1 for latest and use LATEST_VERSION