fix(rest): return 400 for missing required request parameters instead of 500

[Shivamrut]

Fixes #3776

Summary

• MissingServletRequestParameterException extends ServletRequestBindingException → BindException → Exception (not RuntimeException), causing it to bypass the RuntimeException → 400 handler and fall into the catch-all Exception → 500 handler in RestExceptionHandler
• Similarly, MissingServletRequestPartException (thrown for missing multipart file parameters) follows the same inheritance chain and was also incorrectly returning 500
• Added a dedicated handler for both MissingServletRequestParameterException and MissingServletRequestPartException that correctly returns 400 Bad Request
• Imports added accordingly

Screenshot

Before:

After:

Test plan

• Send GET /api/attachments with no sha1 query parameter
• Verify response is now 400 Bad Request with message Required request parameter 'sha1' for method parameter type String is not present
• Verify GET /api/attachments?sha1=<valid_hash> still works correctly and returns 200
• Verify other existing exception handler behaviours are unaffected

Related Direct Fixes

Query Parameter Endpoints (MissingServletRequestParameterException)

Endpoint	Missing Parameter
GET /api/attachments	sha1
POST /api/moderationrequest/validate	entityType or entityId
POST /api/departments/writePathFolder	pathFolder
GET /api/reports	module
GET /api/reports/download	module or token
PATCH /api/releases/mergereleases	mergeTargetId or mergeSourceId
PATCH /api/vendors/mergeVendors	mergeTargetId or mergeSourceId
GET /api/schedule/status	serviceName

Multipart File Endpoints (MissingServletRequestPartException)

Endpoint	Missing Parameter
POST /api/attachments	files
POST /api/importExport/uploadComponent	file
POST /api/importExport/uploadRelease	file
POST /api/importExport/componentAttachment	file

All these endpoints previously returned 500 Internal Server Error instead of 400 Bad Request for missing parameters.

[GMishx]

@Shivamrut please squash all 6 commits into one. This PR works on a single fix and thus, there should be only 1 commit.

[Shivamrut]

@GMishx Thanks for review. I have squashed all commits. Anymore changes required please let me know.