Repair wp/6.8 branch Actions: Fix flaky DataViews list-layout keyboard e2e tests - #83640

Part of #82786.

What?

Stabilizes test/e2e/specs/site-editor/dataviews-list-layout-keyboard.spec.js with two upstream fixes, plus a third upstream fix that the second one needs on this branch:

1. Waits in beforeEach for the Pages list to finish loading (the "Add filter" button and the grid) before any keyboard input, and drops the per-test grid waits this replaces.
2. Deletes all pages in the end-to-end global setup, and renames the spec's two pages from "Privacy Policy" and "Sample Page" to "Page One" and "Page Two".
3. Makes test/e2e/specs/site-editor/template-hierarchy.spec.js create its own front page instead of using page ID 2, the "Sample Page" WordPress creates on install.

Why?

1. The "Add filter" button is only enabled once the post type's fields load, and the pages only appear after a REST request, so a Tab press sent before then can land on the wrong element.
2. WordPress creates "Privacy Policy" and "Sample Page" pages on install, and this spec creates two more with the same titles. The list can then hold two or four pages, and a locator such as "Sample Page" can match two rows.
3. Deleting all pages in the global setup removes "Sample Page", so without this change the Template hierarchy test times out waiting for the front page dropdown on the Reading settings screen.

This spec hasn't failed in the last 48 end-to-end runs on this stack, but it has the same setup as on wp/7.0, where it failed 8 of 100 runs. It's included here for consistency.

Upstream

Ports 99043f7 (#78054) and bdb1750 (#78503) from trunk, one commit each. On this branch beforeEach comes after afterAll, so the wait is added there, and #78503's renames in the "Search input retains focus while typing" test are left out because this branch doesn't have that test.

The Template hierarchy change ports 9ebe4c6 (#69692), which landed on trunk long before #78503. Upstream also switched that test to check the editor's document bar, a change from #69690 that this branch doesn't have, so the branch's existing Title block check is kept.

Use of AI Tools

This PR was created by Claude Code under my supervision. All code should be treated as AI-produced and not yet reviewed by a human until this PR is marked Ready for Review.

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