Extract 'all modules with module type can be instantiated' shared example

MSP-11145

Extracted so it can be used by pro.
Extract 'payload can be instantiated' shared example

MSP-11145

Extracted so that pro can use it.
Extract 'untested payloads' shared context

MSP-11145

Detects if payloads are untested when using the 'payload can be
instantiated' shared examples.
Extract untested-payloads.log checker spec task action

MSP-11145

Extract the spec task action which errored out if
`log/untested-payloads.log` exists to
`Metasploit::Framework::Spec::UntestedPayloads.define_task`.
Remove unneeded section comment

MSP-11145
Add docs for untested payload testing

MSP-11145

Add docs to rake task, shared examples, and share contexts for how to
use all 3 together.