docker: handle versions generated with git describe --tags --long

[kd7lxl]

In #3539 I noted that I wanted to be able to upgrade docker version tags formatted with git describe --tags --long. The format for this is <latest tag>-<number of commits since tag>-g<commit sha>, meaning the first two parts are sortable and the last part should be ignored.

The docker updater has special handling for commit shas, but it doesn't seem to be needed. To make my case work, I removed the line that filters out tags with commit shas: reject { |tag| commit_sha_suffix?(tag) }. Surprisingly, this didn't break any test cases. Please review this thoroughly!

numeric_from_version() discards commit shas before comparison, so it's safe to leave tags with commits shas in the candidate_tags set:

(byebug) version
"v3.9.0-177-ged5bcde"
(byebug) numeric_version_from(version)
"3.9.0-177"

In this PR, I've changed the comparable_tags_from_registry to select tags that look like a commit sha, since they will be discarded later by numeric_from_version. This adds support for upgrading from tags like v3.9.0-177-ged5bcde to v3.10.0-169-gfe040d3.

Fixes #3539

[thepwagner]

LGTM, one idea for extending the test case (but making the change locally - the test still passes so it is potentially moot).