Migrate issuable form branch chooser alert to Pajamas ViewComponent

What does this MR do and why?

Migrate issuable form branch chooser alert to Pajamas ViewComponent

Related to Migrate to Pajamas::AlertComponent ViewComponen... (#325394 - closed)

Screenshots or screen recordings

Before	After

Snapshot before

<div class="gl-alert gl-alert-warning gl-alert-not-dismissible gl-max-content gl-mt-4">
  <div class="gl-alert-container">
    <div class="gl-alert-content" role="alert">
      <svg class="s16 gl-icon gl-alert-icon gl-alert-icon-no-title" data-testid="warning-icon"><use href="/assets/icons-f305926186cfc3bb530f27269d545937c385578ba62adb0088d74f0d2d02cb56.svg#warning"></use></svg>
      <div class="gl-alert-body">

        <br>
        Review the target project before submitting to avoid exposing private changes.
      </div>
    </div>
  </div>
</div>

Snapshot after

<div class="gl-alert gl-alert-warning gl-alert-not-dismissible gl-max-content gl-mt-4" role="alert">
  <svg class="s16 gl-alert-icon gl-alert-icon-no-title" data-testid="warning-icon"><use href="/assets/icons-f305926186cfc3bb530f27269d545937c385578ba62adb0088d74f0d2d02cb56.svg#warning"></use></svg>
  <div class="gl-alert-content" role="alert">
    <div class="gl-alert-body">

      <br>
      Review the target project before submitting to avoid exposing private changes.

    </div>
  </div>
</div>

How to set up and validate locally

• Go to and issue and create a new merge request on any project screen (http://gdk.test:3000/testg/testp/-/merge_requests/new?merge_request%5Bissue_iid%5D=1&merge_request%5Bsource_branch%5D=1-do-this&merge_request%5Btarget_branch%5D=main)
• On that screen, use the following diff a/app/views/shared/issuable/form/_branch_chooser.html.haml to show the alert

+- visibilityMismatchString = i18n["#{0}#{10}"]

+- if true #source_level < target_level