Pre-order tree-il rewrites are now non-destructive

Pre-order tree-il rewrites are now non-destructive

* module/language/tree-il.scm (pre-order): Re-implement in terms of
  pre-post-order, and rename from pre-order!.

* module/language/tree-il/primitives.scm (expand-primitives): Adapt to
  pre-order change, and rename from expand-primitives!.

* module/language/tree-il/optimize.scm (optimize): Adapt to
  expand-primitives! change, and rename from optimize!.

* module/language/tree-il/compile-glil.scm:
* module/system/repl/common.scm:
* test-suite/tests/cse.test:
* test-suite/tests/peval.test:
* test-suite/tests/tree-il.test: Adapt to expand-primitives and optimize
  changes.