fix(treetable): allow space in editable row fields

[OlimjonovOtabek]

Fixes #16748.

What changed

• Separates TreeTable selectable-row Space handling from Enter handling.
• Allows Space from editable or interactive row descendants to keep native browser behavior without triggering row selection or preventDefault.
• Preserves row-level Space and Enter keyboard selection behavior.

Tests

• Adds TreeTable coverage for Space from input, textarea, select, button, and contenteditable descendants.
• Adds coverage that Space and Enter on the selectable row still select.

Validation

• pnpm exec prettier --check packages/primeng/src/treetable/treetable.ts packages/primeng/src/treetable/treetable.spec.ts
• git diff --check
• pnpm run build:lib
• pnpm run test:unit