…_rules checking (#2327)

When --incompatible_python_disallow_native_rules is enabled, all the
core rules fail with
an error that rules_python should be used. This is incorrect, since the
rules_python rules
are being used. What's happening is
#2257
removed the magic migration tag when pystar is enabled, but the code to
check the tag
was present wasn't removed. This went unnoticed because our CI doesn't
set the migration
flag.

To fix, remove the validation logic entirely. If we're in the
rules_python implementation,
then there is not need to perform this validation. It was just something
copy/pasted from
the original code from Bazel itself.

Also update the bazelrc to always set
--incompatible_python_disallow_native_rules.

Fixes #2326
Fixes #1645

Update the headers and sections for the 0.37.1 release.

…#2350)

PR #2253 broke how the config settings are generated and only generated the
config
setting values for the python version values that we would have the
registered
toolchains for. This PR restores the previous behaviour. However, if the
root
module uses `python.override` to remove the allowed toolchains, then
`config_settings` will be also affected.

(cherry picked from commit 9340a81)

Conflicts:
- CHANGELOG.md