gbl: update EFI protocol documentation

Update the protocol documentation with a bit more structure and
precision about which protocols are required and what they all do.

Also a minor update to the protocol doc test to allow the word
"Protocol" by itself without flagging it as a protocol definition.

Bug: b/359929456
Change-Id: I4bdac9352a1c75ed3c2edda045c44bed722abf2c