cpm: always_download now considers patches json entry

[robertmaynard]

Description

Now we only mark always_download as true when the override is changing the git_tag, git_url, and patches.

Corrects issues where projects like libcudf would add an override for projects with just patches listed and expect
always_download to be true.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.
• The cmake-format.json is up to date with these changes.

[robertmaynard]

/merge