Vendorise packaging.versions.LegacyVersion

[nsoranzo]

from packaging 21.3 .
This allows us to unpin packaging . Fix #15898 .

Additionally:

• Use packaging.version.Version() instead of packaging.version.parse() for parsing versions of Galaxy, Pulsar, conda and conda-build, i.e. assume these are always PEP-440 compliant.
• Use galaxy.tool_util.version.parse_version() (equivalent to packaging.version.parse() from packaging 21.3) for parsing (possibly non-PEP440-compliant) versions of Galaxy tools and conda packages (there is e.g. a samtools-1.2.rglab package in the bioconda channel).

This is the first step to fix the Galaxy tool sorting issue partially addressed by #13570 .

How to test the changes?

(Select all options that apply)

• I've included appropriate automated tests.
• This is a refactoring of components with existing test coverage.
• Instructions for manual testing are as follows:
  1. [add testing steps and prerequisites here if you didn't write automated tests covering all your changes]

License

• I agree to license these and all my past contributions to the core galaxy codebase under the MIT license.

[mvdbeek]

Thank you so much @nsoranzo!