chore: separate Lexical tests into dedicated suite (#12047)

Lexical tests comprise almost half of the collections in the fields
suite, and are starting to become complex to manage.

They are sometimes related to other auxiliary collections, so
refactoring one test sometimes breaks another, seemingly unrelated one.

In addition, the fields suite is very large, taking a long time to
compile. This will make it faster.

Some ideas for future refactorings:
- 3 main collections: defaultFeatures, fully featured, and legacy.
Legacy is the current one that has multiple editors and could later be
migrated to the first two.
- Avoid collections with more than 1 editor.
- Create reseed buttons to restore the editor to certain states, to
avoid a proliferation of collections and documents.
- Reduce the complexity of the three auxiliary collections (text, array,
upload), which are rarely or never used and have many fields designed
for tests in the fields suite.

test/lexical/collections/Text/shared.ts

@@ -0,0 +1,15 @@
+import type { RequiredDataFromCollection } from 'payload/types'
+
+import type { TextField } from '../../payload-types.js'
+
+export const defaultText = 'default-text'
+export const textFieldsSlug = 'text-fields'
+
+export const textDoc: RequiredDataFromCollection<TextField> = {
+  text: 'Seeded text document',
+  localizedText: 'Localized text',
+}
+
+export const anotherTextDoc: RequiredDataFromCollection<TextField> = {
+  text: 'Another text document',
+}