moving LastWrittenLSNCache to Neon Extension

[thesuhas]

Problem

We currently have this code duplicated across different PG versions. Moving this to an extension would reduce duplication and simplify maintenance.

Summary of changes

Moving the LastWrittenLSN code from PG versions to the Neon extension and linking it with hooks

Closes: #10973

[github-actions]

If this PR added a GUC in the Postgres fork or neon extension,
please regenerate the Postgres settings in the cloud repo:

make NEON_WORKDIR=path/to/neon/checkout \
  -C goapp/internal/shareddomain/postgres generate

If you're an external contributor, a Neon employee will assist in
making sure this step is done.

[github-actions]

7744 tests run: 7357 passed, 9 failed, 378 skipped (full report)

---

Failures on Postgres 17

• test_postgres_version: release-x86-64-without-lfc, release-x86-64-with-lfc, debug-x86-64-without-lfc, release-arm64-without-lfc, release-arm64-with-lfc

Failures on Postgres 16

• test_postgres_version: release-x86-64-with-lfc, release-arm64-with-lfc

Failures on Postgres 15

• test_postgres_version: release-x86-64-with-lfc, release-arm64-with-lfc

# Run all failed tests locally:
scripts/pytest -vv -n $(nproc) -k "test_postgres_version[release-pg15] or test_postgres_version[release-pg15] or test_postgres_version[release-pg16] or test_postgres_version[release-pg16] or test_postgres_version[release-pg17] or test_postgres_version[release-pg17] or test_postgres_version[debug-pg17] or test_postgres_version[release-pg17] or test_postgres_version[release-pg17]"

Flaky tests (1)

Postgres 15

• test_sharding_compaction[4-32768-True]: release-arm64-with-lfc

Test coverage report is not available

_{The comment gets automatically updated with the latest test results
e4f8d9c at 2025-02-27T23:47:47.906Z :recycle:}

[tristan957]

Let's expand lwlsn to last written lsn