Update filing endpoints to block when filing is in CLOSED state

[guffee23]

In #533, the implementation of an OPEN and CLOSED state was added.
In the filing_validators.py, use the state of the filing to prevent use of the following endpoints if the state is CLOSED:

• /post_filing
• /sign_filing (this was handled in Prototype new Filing status #533)
• /upload_file
• /accept_submission
• /put_institution_snapshot
• /update_task_state
• /put_contact_info
• /update_is_voluntary
• /reopen_filing (this was handled in Prototype new Filing status #533)

In the filing_validators.py, implement a different way to handle error messages when the validator throws an error. Currently, validations are duplicated for the sake of more accurate error responses. Change this to reduce the redundancy of the validations while still providing accurate messaging.

[guffee23]

The filing validator error handling changes have been moved to #558.