Update devfile dropdown with file selection option and .devfile.yaml/yml

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MR: Pending

Description

After we released the devfile dropdown, we have discussions on slack about its further updates. https://gitlab.slack.com/archives/C03KE0L9NC9/p1739261801776849?thread_ts=1738954674.921079&cid=C03KE0L9NC9

And the plan is to add a file selection option, and also include all .*devfile*.yaml/yml devfiles at the root directory.

Acceptance criteria

• add the file search option in devfile dropdown
• include all .*devfile*.yaml/yml devfiles at the root directory into the dropdown option
• make the API hardcoded to a fixed values on return, and remove infinite scrolling
• add metrics for the user usage on both backend and frontend for events below, #519488 (comment 2372159072)

Implementation plan

For file selection option, the GlCollapsibleListbox already have support, and we just need to enable searchable attribute on the component. https://gitlab-org.gitlab.io/gitlab-ui/?path=/docs/base-dropdown-collapsible-listbox--docs#search, see the comment below for more design details, #519488 (comment 2346154028)

Update the root directory API call to get all files from root (first 200), and do a filter on filename matching .*devfile*.yaml/yml

query {
  project(fullPath:"gitlab-org/gitlab") {
    repository {
      tree {
        blobs(first: 200) {
          nodes {
            path
          }
        }
      }
    }
  }
}