Add "not null" validator for listvalidator, setvalidator, and objectvalidator

[austinvalle]

Terraform CLI and Framework Versions

Terraform v1.3.7
on darwin_arm64

github.com/hashicorp/terraform-plugin-framework v1.1.1

Use Cases or Problem Statement

In relation to blocks, in the SDKv2 you could apply the Required field like so:
https://github.com/hashicorp/terraform-provider-cloudinit/blob/b91da5224dbf17a3302633a3643ebf44c686c148/internal/provider/datasource_cloudinit_config.go#L25

This functionality is currently only present for Attributes as that is preferable over using blocks for newer schema development.

Proposal

• Add a "not null" validator for usage with listvalidator, setvalidator, and objectvalidator
• Document in comments + migration guide that this validator is typically only for usage with blocks, otherwise you should use the Required field.

Additional Information

N/A

Code of Conduct

• I agree to follow this project's Code of Conduct

[github-actions]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.
If you have found a problem that seems similar to this, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.