Fixed various carbon displays

[marcusmoore]

This PR fixes display issues around eol dates and rates.

We have to update Carbon diffIn calls now that we're on v3.

For example...
before:

after:

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Note there is one place where I didn't make the change, the DenormalizedEolAndAddColumnForExplicitDateToAssets migration. I think the logic doesn't need to be updated there (since it's not displaying data).

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Fixes #16452

[what-the-diff]

PR Summary

• Enforced Consistent Time Calculations
  This update enforces integer (whole number) time calculations in several controllers and observers, ensuring a consistent approach across the system.

• Refined End-Of-Life (EOL) Month Calculations
  End-of-life calculations, which help determine when an asset will no longer be effective or useful, have been enhanced and now always return whole numbers.

• Updated Display Views
  Various display views have been adjusted to show the improved, integer-based time differences for EOL months and upcoming audits.

• Added Maintenance Functionality Tests
  New tests have been added to ensure that creating and updating asset maintenance details behave as expected and manage the database entries effectively.

• Improved Testing for Asset Processes
  Existing test files have been updated to ensure that the time differences for asset checking in and checking out processes are accurately captured as whole numbers.