Bump min Catch2 version to 3.4.0

[nilsvu]

Proposed changes

We used some features introduced in v3.3.0 by accident.

Upgrade instructions

Building unit tests requires Catch2 v3.4.0 now. See the Catch2 docs for installation instructions (it's a standard CMake configure-build-install).

Code review checklist

• The code is documented and the documentation renders correctly. Run
  make doc to generate the documentation locally into BUILD_DIR/docs/html.
  Then open index.html.
• The code follows the stylistic and code quality guidelines listed in the
  code review guide.
• The PR lists upgrade instructions and is labeled bugfix or
  new feature if appropriate.

Further comments

[knelli2]

Wheeler, CaltechHPC, and Ocean now all have Catch2 v3.4 modules that can be used. I talked to @geoffrey4444 and there will be a separate PR to update the ocean modules.