Fix template support.

- Fix template applying to function name without a starting N.
- Fix return types for templates handling.
- Add support for the T substitution parameter.
- Fix a case where the literal L handler was not being set properly.

Bug: 67678053

Test: New unit tests, fuzzer.
Change-Id: I4f831038047eb2cd8519426f16aa2bdcb846d92d
3 files changed