refactor(dropdowns): use transient props + snapshot testing [DO NOT MERGE]

[ze-flo]

⚠️ DO NOT MERGE! ⚠️

Description

This PR adds snapshot tests for our buttons, forms, dropdowns.legacy, and dropdown stories. These tests capture the current visual appearance of the stories before making changes to transient props.

This helps ensure that the refactoring work in #1961 doesn't accidentally introduce any visual bugs. Identical snapshots taken before and after the changes should give reviewers more confidence that no regressions were introduced.

[ze-flo]

The changes fixed a misalignment of the MenuItem icon when isCompact is true.

The top offset should be 6px.

https://github.com/zendeskgarden/react-components/actions/runs/11490069603/job/31980284923?pr=1962#step:6:1288

FAIL packages/dropdowns/demo/stories/MenuStory.spec.tsx
  ● MenuStory Component › renders MenuStory with compact styling, an arrow, and expanded state

    expect(received).toMatchSnapshot()

    Snapshot name: `MenuStory Component renders MenuStory with compact styling, an arrow, and expanded state 1`

    - Snapshot  - 1
    + Received  + 1

    @@ -416,11 +416,11 @@

      .c14 {
        position: absolute;
        -webkit-transition: opacity 0.1s ease-in-out;
        transition: opacity 0.1s ease-in-out;
    -   top: 10px;
    +   top: 6px;
        left: 12px;
        width: 16px;
        height: 16px;
        opacity: 0;
        color: #1f73b7;

       7 | const renderAndMatchSnapshot = (props: any) => {
       8 |   const { container } = render(<MenuStory {...props} />);
    >  9 |   expect(container.firstChild).toMatchSnapshot();
         |                                ^
      10 | };
      11 |
      12 | const mockItems: Items = [

      at toMatchSnapshot (packages/dropdowns/demo/stories/MenuStory.spec.tsx:9:32)
      at Object.renderAndMatchSnapshot (packages/dropdowns/demo/stories/MenuStory.spec.tsx:88:5)

  ● MenuStory Component › renders MenuStory with all custom props

    expect(received).toMatchSnapshot()

    Snapshot name: `MenuStory Component renders MenuStory with all custom props 1`

    - Snapshot  - 1
    + Received  + 1

    @@ -416,11 +416,11 @@

      .c14 {
        position: absolute;
        -webkit-transition: opacity 0.1s ease-in-out;
        transition: opacity 0.1s ease-in-out;
    -   top: 10px;
    +   top: 6px;
        left: 12px;
        width: 16px;
        height: 16px;
        opacity: 0;
        color: #1f73b7;

I will update the snapshots and use them as reference.

[coveralls]

coverage: 95.891%. remained the same
when pulling ae9e4f2 on ze-flo/transient-props-dropdowns-with-specs
into 5a6c53c on main.

[ze-flo]

Closing since #1961 merged.