GHA: scan git repository and detect unvetted binary files

The only binary-looking files that are accepted in the git repository
need to match the checksums in the sha256sum file
".gi

GHA: scan git repository and detect unvetted binary files

The only binary-looking files that are accepted in the git repository
need to match the checksums in the sha256sum file
".github/scripts/binarycheck.sums".

This is done to make sure that no one has planted any hidden (encrypted)
potentially dangerous payload in the tree.

Closes #14333

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