Add a reset-test-env ddev host command for easier contributor setup

Problem/Motivation

In #3586777: Install ddev/ddev-drupal-contrib 1.1.5 and #3586798: Add drush to the development environment, we added some DDEV tooling to make it easier to set up Feedback for contributing.

In a similar issue for another module, @boromino and @mparker17 came up with a script to further simplify setting up the module for development: a custom ddev reset-test-env command to install dependencies, re-install Drupal and the module, and display a link that contributors can use to log into the test site.

This seems like a useful addition to Feedback, so lets port that custom command to this module.

Proposed resolution

Add a .ddev/commands/host/reset-test-env file that looks like...

#!/bin/bash
ddev poser
ddev exec "cd web/core && yarn install"
ddev symlink-project
ddev drush -y site:install standard
ddev drush -y pm:install feedback
ddev drush -y uli

Once this issue is merged, update the documentation accordingly.

Remaining tasks

1. Merge request - merge request !14 created by @mparker17 in #2
2. Community/maintainer review - skipped by @mparker17 in #3
3. Commit - merged by @mparker17 in #4
4. Update docs - done by @mparker17 in #5
5. Release

User interface changes

None.

API changes

None.

Data model changes

None.