Built expression translators for DateDiff implementations for TimeSpan

[WhitWaldo]

Please check if the PR fulfills these requirements

• The code builds and tests pass (verified by our automated build checks)
  The code builds in the EFCore.SqlServer project which is the only place I made changes. Was unable to get the rest of the solution to build (but I couldn't get the original fork to either with the same errors).

• Commit messages follow this format

    Summary of the changes
    - Detail 1
    - Detail 2

    Fixes #14685  

• Tests for the changes have been added (for bug fixes / features)
  Didn't see any existing unit tests to complement with my changes.

• Code meets the expectations our engineering guidelines. https://github.com/aspnet/Home/wiki/Engineering-guidelines.

Please review the guidelines for CONTRIBUTING.md for more details.

[dnfclas]

All CLA requirements met.

[ajcvickers]

@WhitWaldo We're going to hold off on this for a while since there are major updates happening in the query pipeline for 3.0. We'll consider it once this work is merged. However, please make sure to add tests.

[smitpatel]

Superseded by #15810