Automatically update provider version in coder/coder upon release

# Problem

In `coder/coder` and `coder/modules`, we reference the `coder/coder` Terraform provider version in multiple places (https://github.com/coder/coder/pull/16309#pullrequestreview-2580241216)

* `provisioner/terraform/testdata`
* `examples/templates/*`
* all of our modules in `coder/modules`

When a new version of the Terraform provider is released, we currently do not have any way of updating references to the provider version we reference in `coder/coder`. We currently just "handwave" it by:

1) Not specifying a version at all (most example templates)
2) Specifying `>= 0.x` (in our modules)
3) Specifying provider version `~> 1.0.0` (2 example templates)

This leads to significant version sprawl and makes it difficult to make informed decisions about what version of the provider is actually in use.

# Proposed Solution

> A better option would be to set version constraints that we auto-bump when new provider versions are released.

We could possibly couple this to the release workflow of the provider:
* After a release, clone the Coder repo at main
* Run a script that updates the provider version in the required places
* Commit and push a branch, and create a PR on coder/coder

_Originally posted by @johnstcn in https://github.com/coder/coder/issues/16309#issuecomment-2621308491_

Review the provider release workflow and the referenced locations in provisioner/terraform/testdata, examples/templates/*, and coder/modules. Determine how provider releases can trigger an update across those references and what repository permissions and validation are needed. Done means a released provider version produces an automated branch and pull request with all intended references updated.

Written by the indexing model from the issue text.