Resolve ""400 Bad Request" during authentication due to password format (length or special chars)"

What does this MR do?

Due to recent changes authorization through command line when password include special characters was returning 400 error.

I have added changes that handle credentials slightly differently in lib/gitlab/middleware/handle_malformed_strings.rb rack middleware.

Screenshots (strongly suggested)

before:

After:

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Related to #285076 (closed) and #288324 (closed)