[EuiDataGrid] Fix paginated & height-limited datagrids becoming unscrollable on rowCount change

[cee-chen]

Summary

• closes [EuiDataGrid] Vertical scroll becomes disabled with pagination and content change #5391
• Bug introduced in [EuiDataGrid] Allow the grid to expand & contract with changing rowCount values #5313

Problem

eui/src/components/datagrid/body/data_grid_body.tsx

Line 601 in a648149

setHeight(undefined);

height being set to undefined means that finalHeight falls back to unconstrainedHeight here on line 641:

eui/src/components/datagrid/body/data_grid_body.tsx

Lines 639 to 641 in cb9f462

	let finalHeight = IS_JEST_ENVIRONMENT
	? Number.MAX_SAFE_INTEGER
	: height || unconstrainedHeight;

Which leads to .euiDataGrid__virtualized and the inner content being the same unconstrainedHeight, resulting in inner content that never scrolls:

Before

before.mp4

Solution

Having the main setHeight() logic (lines 604-608) respond dynamically to rowCount fixes the issue. I did some testing and was also fairly sure that the setHeight(undefined) line was unnecessary and that just adding rowCount as a dependency/side effect of determining the wrapper height was sufficient to solve the initial issue in #5313, but would appreciate a confirmation of that @chandlerprall!

After

after.mp4

Regression testing

regression-test.mp4

Checklist

- [ ] Check against all themes for compatibility in both light and dark modes
- [ ] Checked in mobile

• Checked in Chrome, Safari, Edge, and Firefox

NOTE: Heights are still not working quite the same on my local Firefox as on Chrome, but we ascertained this appears to be individual to my Firefox in #5313 (comment)

- [ ] Props have proper autodocs and playground toggles
- [ ] Added documentation
- [ ] Checked Code Sandbox works for any docs examples

• Added or updated jest and cypress tests

Not 100% sure about adding tests for this as #5391 did not have any

- [ ] Checked for breaking changes and labeled appropriately
- [ ] Checked for accessibility including keyboard-only and screenreader modes

• A changelog entry exists and is marked appropriately

[kibanamachine]

Preview documentation changes for this PR: https://eui.elastic.co/pr_5400/

[chandlerprall]

LGTM! Talked through the change together & paired on testing in the PR's deployed docs.

Please remove the row count range before merging.

[kibanamachine]

Preview documentation changes for this PR: https://eui.elastic.co/pr_5400/