Prompt user to create a canvas.config.json with componentDir defined if it does not exist
>>> [!note] Migrated issue
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<!-- Migrated from issue #3580523. -->
Reported by: [longwave](https://www.drupal.org/user/246492)
Related to !772 !769
>>>
<h3 id="overview">Overview</h3>
<p>We need to know the <code>componentDir</code> - there was already code to prompt for this but it was never used.</p>
<p>Broken out from <span class="drupalorg-gitlab-issue-link drupalorg-gitlab-link-wrapper"><a href="https://git.drupalcode.org/project/canvas/-/work_items/3580302" class="drupalorg-gitlab-link">https://git.drupalcode.org/project/canvas/-/work_items/3580302</a></span>, as this is getting more complicated, and we can clean up some code while we're here.</p>
<h3 id="proposed-resolution">Proposed resolution</h3>
<p>Do not default <code>componentDir</code><br>
Prompt for it if not set<br>
Handle the legacy environment variable in the same place</p>
<h3 id="ui-changes">User interface changes</h3>
issue