Draft: Add filtering and sorting parameters to the subscriptions list command

Related Issue(s):

Closes #

Proposed Changes:

For inclusion in changelog (if applicable):

Not intended for changelog:

Diff of User Interface

Old behavior:

New behavior:

PR Checklist:

[] This PR is as small and focused as possible
[] If this PR includes proposed changes for inclusion in the changelog, the title of this PR summarizes those changes and is ready for inclusion in the Changelog.
[] I have updated docstrings for function changes and docs in the 'docs' folder for user interface / behavior changes
[] This PR does not break any examples or I have updated them

(Optional) @mentions for Notifications:

planetlabs / planet-client-python