Add Percona pg_tde (TDE) Dockerfile for postgres 17.9 bookworm

[souravbiswassanto]

Adds tde/17.9/bookworm/Dockerfile, following the same layout convention as the
existing ext/<version>/<distro>/ and dhi/<version>/<distro>/ trees, so the
builder can produce a 17.9-percona tag.

What it is

Percona Server for PostgreSQL 17.9 + pg_tde.
KubeDB's Transparent Data Encryption support needs pg_tde, whose tde_heap
access method only works on the Percona fork — not community PostgreSQL — so it
cannot run on the stock postgres:<major>-bookworm image.

The Dockerfile keeps the exact runtime contract KubeDB already relies on:

• postgres user/group at uid/gid 999
• server binaries on PATH at /usr/lib/postgresql/17/bin
• upstream docker-entrypoint.sh, initdb helpers and gosu, copied verbatim
  from ghcr.io/appscode-images/postgres:17.9-bookworm
• identical PGDATA, locale, VOLUME, STOPSIGNAL SIGINT, EXPOSE 5432

Source

Taken from https://github.com/kubedb/postgres-docker/tree/release-17.9-percona
with three changes so it fits this repo and the builder:

1. the entrypoint donor stage is ghcr.io/appscode-images/postgres:17.9-bookworm
   instead of Docker Hub postgres:17-bookworm — matches what the ext
   Dockerfiles do and keeps the minor aligned with the tag
2. PG_VERSION defaults to 2:17.9-1.bookworm (the builder passes no
   --build-arg, so the pin has to be the default for the tag to be truthful)
3. org.opencontainers.image.source label points at this repo

Verified

Built locally for linux/amd64:

postgres (PostgreSQL) 17.9 - Percona Server for PostgreSQL 17.9.1 - Percona Distribution
uid=999(postgres) gid=999(postgres)
pg_tde.control present in /usr/share/postgresql/17/extension/
pg_tde_basebackup, pg_tde_rewind, pg_tde_waldump, pg_tde_resetwal all executable

percona-postgresql-17 / percona-pg-tde17 are published for both amd64 and
arm64 in repo.percona.com/ppg-17/apt (bookworm), and the base image has both
platforms, so the multi-arch builder job is satisfied.

Note on the branch

This branch stacks on 6447b6c (the existing, not-yet-merged ext + dhi
commits), same lineage the ext.json / dhi.json blocks point at, so the diff
against master also shows those earlier files. Only
tde/17.9/bookworm/Dockerfile is new here.

Builder side: appscode-images/builder#109