Add new fields to Postgres to enable Rootless Configuration for Static Roles

[vinay-gopalan]

Description

Adds support for the Vault 1.18+ Ent feature of Rootless Password Rotation and Configuration for Static Roles. Currently the feature is only enabled for the Postgres engine.

Checklist

• Added CHANGELOG entry (only for user-facing changes)
• Acceptance tests where run against all supported Vault Versions

Output from acceptance testing:

$ make testacc TESTARGS='-run=TestAccDatabaseSecretBackendConnection_postgresql_rootlessConfig'
=== RUN   TestAccDatabaseSecretBackendConnection_postgresql_rootlessConfig
    resource_database_secret_backend_connection_test.go:876: Vault server version "1.18.0+ent"
--- PASS: TestAccDatabaseSecretBackendConnection_postgresql_rootlessConfig (0.77s)
PASS

$ make testacc TESTARGS='-run=TestAccDatabaseSecretBackendStaticRole_Rootless'
=== RUN   TestAccDatabaseSecretBackendStaticRole_Rootless
    resource_database_secret_backend_static_role_test.go:172: [TRACE] Creating test user
--- PASS: TestAccDatabaseSecretBackendStaticRole_Rootless (4.82s)
PASS

[fairclothjm]

LGTM!