Allow schema-qualified type names in Grant routine args

[aravinthAS]

Description of your changes

Grant.spec.forProvider.routines[].args validates each argument
against ^[a-zA-Z_][a-zA-Z0-9_$]*$, which rejects any dot. This blocks
granting EXECUTE on routines whose signature includes a
schema-qualified composite type -- e.g. AWS RDS's
aws_s3.table_import_from_s3:

table_import_from_s3(text, text, text, aws_commons._s3_uri_1, aws_commons._aws_credentials_1)

Applying such a Grant fails at admission with:

spec.forProvider.routines[0].args[3]: Invalid value: "aws_commons._s3_uri_1": should match '^[a-zA-Z_][a-zA-Z0-9_$]*$'

There's no way to express this grant today.

Root cause / why this isn't just "widen the regex"

The pattern isn't only shape validation -- it's the SQL-injection guard
for this field. quotedSignatures() in the grant reconciler splices
each argument unquoted directly into the GRANT/REVOKE ... ON ROUTINE SQL string:

// Safe because the CRD restricts arguments to identifier characters:
// +kubebuilder:validation:items:Pattern:=^[a-zA-Z_][a-zA-Z0-9_$]*$
args[j] = strings.ToLower(arg)

So the CRD pattern is the only thing standing between this field and
arbitrary SQL. This PR widens it to allow exactly one optional
schema.type qualification, instead of opening up punctuation
generally:

^[a-zA-Z_][a-zA-Z0-9_$]*(\.[a-zA-Z_][a-zA-Z0-9_$]*)?$

This still anchors start/end and only permits a single well-formed
identifier.identifier shape -- injection payloads (; DROP TABLE ..., embedded quotes/parens, extra dots, etc.) still fail to match.

Changes

• Updated the pattern on Routine.Arguments in both the cluster-scoped
  (apis/cluster/postgresql/v1alpha1/grant_types.go) and namespaced
  (apis/namespaced/postgresql/v1alpha1/grant_types.go) Grant APIs,
  which duplicate this type.
• Updated the safety comment above quotedSignatures() in both
  reconcilers to document the widened invariant.
• Regenerated CRDs via go generate (package/crds/postgresql.sql.crossplane.io_grants.yaml,
  package/crds/postgresql.sql.m.crossplane.io_grants.yaml) -- only
  the routines[].args field changed.
• Added TestRoutineArgumentPattern (new grant_types_test.go in both
  API packages) asserting the pattern accepts schema-qualified
  identifiers and still rejects malformed/injection input.
• Added RoutineArgumentsAllowSchemaQualifiedCompositeTypes to the
  existing TestGrantSQL table (both cluster and namespaced
  reconciler_test.go), asserting the generated GRANT/REVOKE SQL for
  aws_s3.table_import_from_s3 with aws_commons._s3_uri_1 /
  aws_commons._aws_credentials_1 args.

How has this code been tested

• go build ./...
• go test $(go list ./... | grep -v /test/) -- all packages pass
• go vet ./...
• gofmt -l on all changed files -- no output
• Manually verified go generate regenerated only the two Grant CRD
  files, with only the args pattern/description changed

I have:

• Read and followed Crossplane's contribution process.
• Run make reviewable to ensure this PR is ready for review. (ran go build/go test/go vet/gofmt and go generate directly; make reviewable itself wasn't runnable in this environment, see note below)