Make changes and changelog command work with other repos

[nmuesch]

What does this PR do?

Updates the changes and changelog ddev command to allow it to work with other open-source repositories

Motivation

Gain the ability to use the same autogeneration changelog workflow in other projects 😄

Additional Notes

The command invocation wouldn't change for existing integrations, but for other projects would now let you:

ddev release show changes . (Note the lack of a check name at the end, instead is . which would now default to the current working directory)

and

ddev release changelog . <VERSION> (Note the special . character to denote we're not doing a check but the current directory.

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• PR title must be written as a CHANGELOG entry (see why)
• Files changes must correspond to the primary purpose of the PR as described in the title (small unrelated changes should have their own PR)
• PR must have changelog/ and integration/ labels attached

[codecov]

Codecov Report

Merging #5331 into master will decrease coverage by 3.78%.
The diff coverage is 50%.

Impacted Files	Coverage Δ
...checks_dev/datadog_checks/dev/tooling/constants.py	96.29% <100%> (+0.14%)	⬆️
...tadog_checks_dev/datadog_checks/dev/tooling/git.py	93.84% <42.85%> (-6.16%)	⬇️
datadog_checks_dev/tests/test_docker.py	48.14% <0%> (-51.86%)	⬇️
datadog_checks_dev/datadog_checks/dev/docker.py	31.42% <0%> (-31.43%)	⬇️
datadog_checks_dev/datadog_checks/dev/env.py	23.07% <0%> (-28.21%)	⬇️
...atadog_checks_dev/datadog_checks/dev/structures.py	67.79% <0%> (-18.65%)	⬇️
datadog_checks_dev/datadog_checks/dev/_env.py	46.15% <0%> (-18.47%)	⬇️
datadog_checks_dev/tests/test_conditions.py	82.25% <0%> (-17.75%)	⬇️
...atadog_checks_dev/datadog_checks/dev/subprocess.py	62.16% <0%> (-16.22%)	⬇️
...atadog_checks_dev/datadog_checks/dev/conditions.py	80.95% <0%> (-4.77%)	⬇️
... and 829 more