Resolve "Monitoring graph date formatting is wrong"

What does this MR do?

Fixes two bugs with date/time formatting on the ~Prometheus monitoring graphs:

1. Hours are formatted 24-hour (%H) instead of 12-hour (%I) despite having an AM/PM suffix.
2. Hours and days are prefixed with zeros on time axes.

Screenshots (if relevant)

Before	After

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together

What are the relevant issue numbers?

Closes #37104 (closed)