Cleanups

[pstradomski]

Minor cleanups:

• rename experimental/rules_python to experimental/tools to avoid confusion,
• change "generator" header in distinfo/WHEEL to be more informative.

PR Checklist

Please check if your PR fulfills the following requirements:

• Does not include precompiled binaries, eg. .par files. See CONTRIBUTING.md for info
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature (please, look at the "Scope of the project" section in the README.md file)
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• Other... Minor cleanups

What is the new behavior?

Change in "generator" header in distinfo/WHEEL

Does this PR introduce a breaking change?

• Yes
• No

[thundergolfer]

👍