[FEAT]: Support write-only (ephemeral) values for GitHub environment secrets in Terraform

### Describe the need

### Summary
We need to create GitHub environment secrets via Terraform without persisting sensitive values in state.

### Problem
Terraform now supports ephemeral values, which allows generating secrets without statefile persistence. However, the GitHub provider does not support write-only (_wo) arguments for secrets, so any secret value passed to github_actions_environment_secret is stored in the Terraform state.

### Why this matters
This prevents using Terraform to manage GitHub environment secrets in a secure, state-free way, even when the secret is generated ephemerally.

### Expected behavior
Allow write-only (or equivalent) secret inputs for GitHub environment secrets so sensitive values are never written to state.

### SDK Version

_No response_

### API Version

_No response_

### Relevant log output

```shell

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### Code of Conduct

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