Fix DBX JSON schema

[cjee21]

Description

PreSignedObjects\DBX\HashesJsonSchema.json does not accurately describe PreSignedObjects\DBX\dbx_info_msft_latest.json and fails validation. This PR fixes the schema to accurately describe the JSON and enables it to pass validation. The schema is also updated to 2020-12 and format checking is enabled in the validate_schema Python script to validate the format of dates.

Also added DBX JSON schema validation to the CI to ensure both HashesJsonSchema.json and dbx_info_msft_latest.json will remain in sync in the future.

How This Was Tested

>python -m pip install jsonschema[format]
>python scripts\validate_schema.py PreSignedObjects\DBX\dbx_info_msft_latest.json PreSignedObjects\DBX\HashesJsonSchema.json
INFO:root:JSON data is valid against the schema.
INFO:root:JSON data is valid against the schema.

Integration Instructions

N/A

[cjee21]

@microsoft-github-policy-service agree

[Flickdm]

@cjee21 can you fix the ruff checks?

[cjee21]

@cjee21 can you fix the ruff checks?

Done. Added JSON schema validation to the CI as well.