Implement GetSConsVersion static method

[Repiteo]

Solves a problem brought up in the SCons Discord about a lack of public api for the current version. Also adds some type hints, as a treat.

Contributor Checklist:

• I have created a new test or updated the unit tests to cover the new/changed functionality.
• I have updated CHANGES.txt (and read the README.rst)
• I have updated the appropriate documentation

[Repiteo]

Not entirely convinced this implementation is the way to go; gonna look at some more examples before digging too deep into this. Marking as a draft for the time being.

[bdbaddog]

Looks decent to me. Just needs a test. BTW version string can also have post1, and other version strings allowed by pypi..

[Repiteo]

That sort of inconsistency is part of why I think a more thorough implementation would be preferable. Something more along the lines of how python has the more robust sys.version_info. Being able to account for fringe situations would make this feel like a proper addition, instead of just making it less hacky to grab an existing piece of api.

[bdbaddog]

I'd think you'd most likely be checking for major.minor.patch and the rest could be ignored?
At least for SCons releases, post releases are usually just packaging issues. I'd never release a post with functional differences.

[Repiteo]

I suppose that's fair, yeah. If I wanted to brainstorm something more, that'd probably go beyond the original scope of this PR. I'll get some tests up and running then undraft.

[bdbaddog]

Can you add a blurb in the manpage and (maybe) users guide?
Here's where the manpage blurb would go: https://github.com/SCons/scons/blob/master/SCons/Script/SConscript.xml#L109

User's guide: https://github.com/SCons/scons/blob/master/doc/user/misc.xml#L112

[mwichmann]

The test for EnsureSConsVersion isn't happy now...

 TypeError: SConsEnvironment.EnsureSConsVersion() missing 1 required positional argument: 'minor':
  File "/tmp/testcmd.12132.jsexfe1p/SConstruct", line 2:
    env.EnsureSConsVersion(env.GetSConsVersion())


FAILED test of /home/runner/work/scons/scons/scripts/scons.py
	at line 673 of /home/runner/work/scons/scons/testing/framework/TestCommon.py (_complete)
	from line 775 of /home/runner/work/scons/scons/testing/framework/TestCommon.py (run)
	from line 458 of /home/runner/work/scons/scons/testing/framework/TestSCons.py (run)
	from line 72 of /home/runner/work/scons/scons/test/EnsureSConsVersion.py

[Repiteo]

Ahhh, silly me; I passed in the raw tuple instead of a broken-down version. Maybe I can add an overload to accept a tuple instead? Either way, it's an easy fix.

[Repiteo]

Haven't updated docs before so I'm unsure what I did wrong to make the test fail.

EDIT: Oh, duh. Needed to upload the generated files too. Probably.

EDIT2: Nevermind, I'm lost.