ci: Require upload dates to be valid to schedule package for removal

[matthewfeickert]

Resolves #73

To guard against invalid dates being viewed as being older than the removal threshold date (c.f. numpy/numpy#25907 (comment)) first check that the upload date is YYYY-MM-DD formatted. If not, warn in the logs and skip the offending package.

[MridulS]

The first attempt on remove-old-wheels action was a API failure right?

[matthewfeickert]

The first attempt on remove-old-wheels action was a API failure right?

The error was on the cleanup step of the upload CI, but it was a an API failure

  anaconda --token *** remove \
    --force \
    "scientific-python-nightly-wheels/test-package"
  shell: /usr/bin/bash -l {0}
  env:
    MAMBA_ROOT_PREFIX: /home/runner/micromamba
    MAMBA_EXE: /home/runner/micromamba-bin/micromamba
    CONDARC: /home/runner/work/_temp/setup-micromamba/.condarc
Using Anaconda API: https://api.anaconda.org
Error: [ERROR] ('?: Undefined error ([DELETE] https://api.anaconda.org/package/scientific-python-nightly-wheels/test-package -> 524)', 524)
Error: Process completed with exit code 1.

but as this was a cleanup step and clearly an API failure on Anaconda Cloud's side this was fixed by just retriggering.