feat(postgresql): add forceDrop option to DROP DATABASE

[nicolasburtey]

Summary

Adds an opt-in forceDrop field to the PostgreSQL Database managed
resource that makes the controller issue DROP DATABASE IF EXISTS <name> WITH (FORCE) instead of a bare drop. Applies to both the cluster-scoped
(postgresql.sql.crossplane.io) and namespaced
(postgresql.sql.m.crossplane.io) APIs.

WITH (FORCE) (PostgreSQL 13+) terminates every backend connected to
the target database before dropping it. Without it, a Database with
deletionPolicy: Delete cannot be removed while any client holds an
open connection, because the bare drop fails with SQLSTATE 55006
(object_in_use). The managed resource then sticks Terminating
indefinitely — i.e. provider-sql cannot delete what it created whenever
an application maintains a persistent connection pool against the
database.

Today, Database.Delete is:

err := c.db.Exec(ctx, xsql.Query{String: "DROP DATABASE IF EXISTS " + pq.QuoteIdentifier(meta.GetExternalName(mg))})

This adds the WITH (FORCE) escape hatch so a declarative
deletionPolicy: Delete works even with a live pool.

Design

• New optional boolean spec.forProvider.forceDrop (defaults to
  omitted/false → behaviour unchanged).
• When true, Delete appends WITH (FORCE).
• Version-gated on PostgreSQL 13+ (server_version_num >= 130000),
  returning a clear error otherwise. This mirrors the existing
  create-time strategy version guard.
• forceDrop is a delete-only behaviour toggle, not an observable
  property of the database, so it is added to the upToDate ignore list
  alongside template and strategy (no reconciliation churn).

Open questions for reviewers

• Error vs. fallback on PG < 13. This PR errors when forceDrop is
  requested on a server older than 13, matching strategy. A gentler
  alternative would be to fall back to a pg_terminate_backend drain
  step (works on all versions) when WITH (FORCE) is unavailable. Happy
  to switch to that if preferred. Note PostgreSQL 13 reached EOL in Nov
  2025, so most deployments are already on 14+.
• Naming. Went with forceDrop to map directly to the SQL keyword
  and stay consistent with the existing camelCase field style. Open to
  force / forceDelete if there's a preferred convention.

Validation

• CRDs and deepcopy regenerated via controller-gen.
• Unit tests added for: default bare drop, WITH (FORCE) drop, and the
  unsupported-version error path (cluster + namespaced).
• gofmt, go vet, go build ./..., and go test ./... all pass.

Example

apiVersion: postgresql.sql.crossplane.io/v1alpha1
kind: Database
metadata:
  name: force-drop-db
spec:
  forProvider:
    # Optional, only affects deletion, PostgreSQL 13+.
    forceDrop: true

Draft until I get a 👍 on the error-vs-fallback and naming questions above.