[Feature request] Remove the functionality of `az feedback`

**Related command**
`az feedback`

**Is your feature request related to a problem? Please describe.**

- https://github.com/Azure/azure-cli/pull/25286 stopped including error message in `az feedback`'s feedback body.
- https://github.com/Azure/azure-cli/pull/26459 stopped prompting `az feedback`.

`az feedback` is now half-deprecated.

**Describe the solution you'd like**
Since https://github.com/Azure/azure-cli/pull/26463 refined the GitHub issue template: https://github.com/Azure/azure-cli/issues/new?assignees=&labels=bug&projects=&template=Bug_report.yml, `az feedback` should now just open https://github.com/Azure/azure-cli/issues/new/choose without letting the user select any command. (**🚀Feature request** is also considered a type of feedback.)

**Describe alternatives you've considered**
Totally remove `az feedback`.

**Additional context**
`az feedback`'s test relies on an old extension `alias`:

https://github.com/Azure/azure-cli/blob/4c0f6483633908c0a952a26d8e9e8b1b9c2c7c3d/src/azure-cli/azure/cli/command_modules/feedback/tests/latest/test_feedback.py#L61

This `alias` has packaging issues.