Move the bloat-check-and-CI-specific scripts dir inside .github (#442)

In downstream `rs-matter-stack` and `rs-matter-embassy` this is already
done.

The rationale for this is that - other than for supporting the
CI-specific "Size-Check" action, which was copied from the Python-rich
C++ SDK - we have **no** other use of any Python scripts and we
**don't** author or encourage authoring scripts in Python, for the
purposes of `rs-matter`.

Rather, `rs-matter` prefers **Rust-native** scripting in the form of
`xtask`s, where the `rs-matter` `xtask` project actually keeps growing.

Moving these "copied-over" Python scripts inside `.github` rather than
in a top-level "scripts" directory would thus provide the more correct
message to newcomers that these are not something "standard" for this
project.

Author: ivmarkov

.github/actions/setup-size-reports/action.yaml

@@ -14,4 +14,4 @@ runs:
     shell: bash
     env:
       GH_CONTEXT: ${{ inputs.gh-context }}
-    run: python scripts/memory/gh_sizes_environment.py "${GH_CONTEXT}"
+    run: python .github/scripts/memory/gh_sizes_environment.py "${GH_CONTEXT}"