Opensuse 3.6 gh action - #2

Backport the relevant behavior changes from bpo-45436 (4fe454c),
bpo-41306 (aecf036), and the bpo-45979 correction (dbbe4d2).

Retain the older Tk expectations. On Tk 8.6.11+, explicitly test empty
Menu.type and ttk compound values while still rejecting invalid enum
values. On Tk 8.6.10+, expect Scale.from to retain its fractional value.

Validated test_tk and test_ttk_guionly with Python 3.6 and Tcl/Tk 8.6.12
on openSUSE Leap 15.6, including the affected widget classes with
wantobjects disabled.

Regenerate configure and pyconfig.h.in before the full build so locale
coercion is enabled. Install glibc-locale-base for the UTF-32 converters
required by GDB.

Replace the public HTTP endpoint in test_issue16464 with a mocked
transport while retaining request and Content-Length checks. Include
full GDB command, status and output in failures, with regression
coverage for the diagnostics.

Restore ast.Num and ast.Str handling in Argument Clinic for negative
numeric defaults and legacy string converters.

Use the Python 3.6 Clinic NULL convention for the Unicode escape decoder
error defaults and regenerate their header and checksums. Preserve the
stateful decoding security fix and final argument.

Add regression tests for numeric defaults, string converters, NULL
defaults, and expression validation. Verified clean regen-all output,
make smelly, and the tool, codec, Unicode, and bytes tests on Leap 15.6.

Add only GITHUB_WORKSPACE to safe.directory in the Git configuration
used by shell steps. The checkout action configures its own temporary
HOME, leaving subsequent Git commands subject to ownership checks.

Use git status and git diff --exit-code for the generated-files check so
repository errors are not misreported as stale generated files.