Let each module name the field group its own resource fields go in, and name every method the way core does

Closes [#3619143].

Four commits on top of 1.x:

1. hook_yoyaku_resource_field_group_info(), so each module names the form section its own resource fields go in. Six placement field names leave src/.
2. Six British spellings.
3. The assignment seam renamed off another module's word, and ~280 comment lines plus 19 operator-facing strings moved to unit/partition. The French moves in the same commit.
4. LockAnchors::SCOPE_PARTITION stores partition instead of section. This is a reinstall — see the note added to capacity-and-holds.md.

yoyaku_placement keeps every one of its own names; only the engine changes.

Local before pushing: phpcs 0 errors 0 warnings, phpstan level 3 [OK], check-translations.php 0 missing, and 16 test classes green including ModuleBoundariesTest, which now allows no exceptions at all.