Upgrade PSQL to v16

[amarin-dspace]

Upgrade of PSQL engine to v16 in ref arch, to avoid running into extended support for v11 (28th of Feb).
Have also introduced a config option to apply maintenance change immediately (like major version upgrade), to avoid waiting for next maintenance window.
Also tested an option to have parameter group(s), but is not part of this PR.
Tested with clean deployment of v16 and also upgrade path from v11(.22) to v16 (downgrade is not supported).

Terraform v1.7.1
on linux_amd64

• provider registry.terraform.io/gavinbunney/kubectl v1.14.0
• provider registry.terraform.io/hashicorp/aws v4.67.0
• provider registry.terraform.io/hashicorp/cloudinit v2.3.3
• provider registry.terraform.io/hashicorp/helm v2.12.1
• provider registry.terraform.io/hashicorp/http v3.4.1
• provider registry.terraform.io/hashicorp/kubernetes v2.25.2
• provider registry.terraform.io/hashicorp/local v2.4.1
• provider registry.terraform.io/hashicorp/null v3.2.2
• provider registry.terraform.io/hashicorp/random v3.6.0
• provider registry.terraform.io/hashicorp/time v0.10.0
• provider registry.terraform.io/hashicorp/tls v4.0.5
• provider registry.terraform.io/terraform-aws-modules/http v2.4.1

[schwichti]

Changes are OK for now.
Generating YAML/JSON examples files by quality gate seems to be broken and needs to be fixed in a follow-up PR.