[test] Fix flaky DocSearch modal screenshots

[LukasTy]

The Argos captures of the DocSearch modal sometimes show the hover state of the MUI X "Overview" link on the start screen. The current master baseline of regression-AppSearch/SearchModalDarkOpen.png has it, and so does https://app.argos-ci.com/mui/material-ui/builds/51991/454471015.

The test now moves the pointer to the top-right corner right after the click that opens the modal. That point is outside the modal at both capture widths, so no hover state gets into a capture.

• Locally, the 4 AppSearch regression tests pass, and the captures are byte-identical with and without the change.
• The same change ran on Bump DocSearch to 5.0.1 #48983. Its Argos build https://app.argos-ci.com/mui/material-ui/builds/52001 shows the "Overview" link without the hover.
• Argos on this PR can show a diff in the Open captures, because the master baseline has the hover. That diff is expected.

Extracted from #48983, so that it can merge before the DocSearch bump.

[code-infra-dashboard]

Deploy preview

https://deploy-preview-49122--material-ui.netlify.app/

Bundle size

Bundle	Parsed size	Gzip size
@mui/material	0B(0.00%)	0B(0.00%)
@mui/lab	0B(0.00%)	0B(0.00%)
@mui/private-theming	0B(0.00%)	0B(0.00%)
@mui/system	0B(0.00%)	0B(0.00%)
@mui/utils	0B(0.00%)	0B(0.00%)

Details of bundle changes

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Check out the code infra dashboard for more information about this PR.

[LukasTy]

Argos marked CrudDashboard.png as "added" on #49122 (https://app.argos-ci.com/mui/material-ui/builds/52015/456363749), but that PR does not touch it. The cause is how our nightly jobs upload to Argos.

What happens:

• The nightly test_regressions-react@18 and test_regressions-react@next jobs upload with the same default build name as the normal test_regressions run.
• Master auto-approves every build, and Argos uses the last approved build on the merge-base commit as the baseline. On 5ce5a0f, that was the nightly React 18 build: https://app.argos-ci.com/mui/material-ui/builds/52007
• Since [test] Skip the CrudDashboard VRT on React 18 #49027, the React 18 run skips CrudDashboard. So that baseline does not have it, and PRs based on that commit show it as added.
• Nightly runs can also change other baselines. Build 52007 changed SearchModalOpen.png too.

Proposal: give the non-stable React runs their own Argos build name. Argos only compares builds with the same name. @argos-ci/core reads ARGOS_BUILD_NAME from the environment, so code-infra and the orb need no change. In the test_regressions job, before code-infra/argos-push:

- when:
    condition:
      not:
        equal: [stable, << parameters.react-version >>]
    steps:
      - run:
          name: Use a separate Argos build name
          # Keeps the React canary runs out of the baseline that PRs compare against.
          command: echo 'export ARGOS_BUILD_NAME="$CIRCLE_JOB"' >> "$BASH_ENV"

Result: the nightly builds become test_regressions-react@18 and test_regressions-react@next, each with its own baseline and its own argos/<name> status. PR builds compare only with the normal master run. Argos also adds an argos/summary check on commits with more than one build.

Questions:

1. Do we need the nightly screenshots in Argos at all? Master auto-approves them, so nobody has to review them. Skipping the upload for non-stable React runs is simpler and uses fewer screenshots, but we lose the nightly visual history.
2. nightly-cron also runs on v5.x, v6.x, and v7.x. Do we want the same change there?