test: add wait for render for the ohif-downstream

[wayfarer3130]

Context

Viewports didn't have a good way to check if they were rendered/up to date, resulting in using waits instead of actively waiting for changes to complete in OHIF and CS3D playwright tests.

This test has no functional change, just adds detection for needs render/rendered state.

Changes & Results

Testing

Checklist

PR

• [] My Pull Request title is descriptive, accurate and follows the
  semantic-release format and guidelines.

Code

• [] My code has been well-documented (function documentation, inline comments,
  etc.)

Public Documentation Updates

• [] The documentation page has been updated as necessary for any public API
  additions or removals.

Tested Environment

• [] "OS:
• [] "Node version:
• [] "Browser:

[jbocce]

I love this initiative. See my comments

[jbocce]

Love the changes.