feat: Add methods to get footer and header cells

[TatuLund]

Fixes #7330

[vaadin-bot]

TC Format Checker Report - 11:16 - 23 - Apr

There are 1 files with format errors

• To see a complete report of formatting issues, download the differences file

• To fix the build, please run mvn spotless:apply in your branch and commit the changes.

• Optionally you might add the following line in your .git/hooks/pre-commit file:

  mvn spotless:apply
  

Here is the list of files with format issues in your PR:

vaadin-grid-flow-parent/vaadin-grid-testbench/src/main/java/com/vaadin/flow/component/grid/testbench/GridElement.java

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud