TestFormatSpec need revision

[UmerShahidengr]

Currently, TestFormatSpec is out of date, and a lot of macors have been added in the test_macros.h and arch_test.h, also ctg and isac have been merged into riscv-arch-tests which has not been mentioned in TestFormatSpec.
This documentation is need to be split in two parts:

1. Explaining the structure of the test, constraints on its size, format and definitions of macros currently being used in the test. (Test Developer Spec)
2. Guide on how to use the tests i.e, which set of macros or labels have to be defined/declared by the user in DUT model_test.h file and/or in DUT plugin. (Test User Spec)

[UmerShahidengr]

Once we finish this one, we have to vote on the changes in SIG-ARCH meeting as previous version of this document was also being voted on.