[rushstack] Restore sha512 integrity hashes in the pnpm 12 lockfiles

The package feed's registry metadata only provides the sha1 `shasum`
for each tarball, not the `integrity` field. PNPM 10 kept the sha512
hashes that were already in the lockfiles, but regenerating the
lockfiles with PNPM 12 re-resolved every package and replaced 3521
sha512 hashes with sha1 hashes (2784 in the default subspace and 737 in
build-tests-subspace).

Restore the sha512 hash from the PNPM 10 lockfile for each of those
packages. The package keys (name, version, and peers) are unchanged, so
the tarballs are identical. Every package now has the same integrity
hash as in the PNPM 10 lockfile. repo-state.json is regenerated.

"rush update" keeps the restored hashes, and "rush install" in CI mode
with an empty PNPM store downloads and verifies every tarball without
changing the lockfiles.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: bmiddha