feat: extract common classes to vaadin-testbench-shared

[MarcinVaadin]

Description

Resurrection of #1318 on latest master

Fixes: #1363

Type of change

• Bugfix
• Feature

Checklist

• I have read the contribution guide: https://vaadin.com/docs/latest/guide/contributing/overview/
• I have added a description following the guideline.
• The issue is created in the corresponding repository and I have referenced it.
• I have added tests to ensure my change is effective and works as intended.
• New and existing tests are passing locally with my change.
• I have performed self-review and corrected misspellings.

Additional for Feature type of change

• Enhancement / new feature was discussed in a corresponding GitHub issue and Acceptance Criteria were created.

[MarcinVaadin]

First run of CI tests often fails - downloading artifacts, building frontend. But second run on same agent is green.

From build log:

[09:11:27][INFO]  T E S T S
[09:11:27][INFO] -------------------------------------------------------
[09:11:27][INFO] Running com.vaadin.tests.PerformanceIT
[09:11:27][WARNING] Tests run: 2, Failures: 0, Errors: 0, Skipped: 2, Time elapsed: 0.386 s - in com.vaadin.tests.PerformanceIT
[09:11:27][INFO] Running com.vaadin.tests.elements.ElementScreenCompareIT
[09:11:47]  
[09:11:47] ------------------ Starting Frontend compilation. ------------------
[09:11:48]  
[09:11:48] ----------------- Frontend compiled successfully. -----------------
[09:11:48]  
[09:11:56][ERROR] Tests run: 1, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 28.319 s <<< FAILURE! - in com.vaadin.tests.elements.ElementScreenCompareIT
[09:11:56][ERROR] elementCompareScreen[Windows_Chrome_](com.vaadin.tests.elements.ElementScreenCompareIT)  Time elapsed: 28.313 s  <<< ERROR!
[09:11:56]org.openqa.selenium.NoSuchElementException:
[09:11:56]No element with tag <button> found using index 4

Please notice that time between test start and frontend compilation start is exactly 20s - timeout hardcoded in TestBenchCommandExecutor.waitForVaadin. Issue occurs after switching to Vite.

Setting -Dsystem.com.vaadin.testbench.Parameters.maxAttempts=2 seems to solve the problem.

Somehow related to #1293

There is already a ticket for that 20s timeout: #1244