[CI] Parallelize visual test runs

[unlikelyzero]

Closes #7615

Describe your changes:

Originally, the intent of this ticket was to make sure we only had one worker per shard. Upon investigation, I discovered that we were already setting workers to 1.
This ticket improves runtime by running the tests in parallel

All Submissions:

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Is this a notable change that will require a special callout in the release notes? For example, will this break compatibility with existing APIs or projects that consume these plugins?

Author Checklist

• Changes address original issue?
• Tests included and/or updated with changes?
• Has this been smoke tested?
• Have you associated this PR with a type: label? Note: this is not necessarily the same as the original issue.
• Have you associated a milestone with this PR? Note: leave blank if unsure.
• Testing instructions included in associated issue OR is this a dependency/testcase change?

Reviewer Checklist

• Changes appear to address issue?
• Reviewer has tested changes by following the provided instructions?
• Changes appear not to be breaking changes?
• Appropriate automated tests included?
• Code style and in-line documentation are appropriate?

[unlikelyzero]

driveby to change the name

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 56.17%. Comparing base (b2b0837) to head (e492a98).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7618      +/-   ##
==========================================
- Coverage   56.58%   56.17%   -0.42%     
==========================================
  Files         672      672              
  Lines       27128    27128              
  Branches     2635     2635              
==========================================
- Hits        15351    15239     -112     
- Misses      11450    11562     +112     
  Partials      327      327              

Flag	Coverage Δ
e2e-full	23.57% <ø> (-24.13%)	⬇️
e2e-stable	59.93% <ø> (+0.02%)	⬆️
unit	49.11% <ø> (+<0.01%)	⬆️

see 12 files with indirect coverage changes

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[scottbell]

LGTM