Add option to remove pattern match failure assertions

In line with the main compiler, we insert pattern match failure assertions (`$runtime.fail()`) when there is no wildcard pattern. Since the pattern matching tree optimizer emits complete if/else trees, we should be able to omit the assertion when a branch covers all tags for a given `ProperName`.

This failure assertion is potentially useful for catching foreign errors sneaking through, so I think this could be an option like `--int-tags`.

Start by locating the pattern matching tree optimizer and the command-line option handling associated with the main compiler and `--int-tags`. Trace where `$runtime.fail()` is emitted for branches without wildcard patterns. Done means the new option controls whether assertions are omitted for complete tag coverage while retaining the option to catch foreign errors.

Written by the indexing model from the issue text.