[BFCL Chore] Add Unit Test for Valid Func Doc Format

[HuanzhiMao]

This PR adds a unit test to check for the correct function doc format. For example, a required parameter should not have a 'default' field.

Below is the output, which indicates potential issues that need to be addressed (they will be fixed in separate PRs).

# python check_func_doc_format.py 
--------------------
Entry ID: exec_multiple_45
Function: book_room
Error: The parameter 'room_type' is of type 'dict' and should contain either 'properties' or 'additionalProperties' field to specify the sub-parameters details.
...

[Fanjia-Yan]

• Remove Commented Code.
• Add instruction to run it on PR description
• List out all possible error cases that could be caught either in codebase or PR description
  Other than that LGTM

[Fanjia-Yan]

LGTM