Documentation - Clearly define what modules AST supports

[CarlB-dev]

Describe the bug
The documentation needs to ensure that users understand which BIG-IP modules that the AST is set to collect data for and what it is not.

Expected behavior
It is implied by the metrics library that AST natively supports/collects data for LTM and ASM/AdvWAF, with the option to enable data collection for GTM/DNS.

Metrics count by Module/Function -
TMOS: 54
Rest: 5
LTM: 215
ASM/AdvWaf: 31
GTM/DNS: 40 (Not enabled by default)

APM: NA
AFM: NA
CGNAT: NA
PEM: NA
Note these counts might be off based on how you might characterize some of the counters, but this is the general idea.