[Parser] Simplify the lexer interface (#6319)

The lexer was previously an iterator over tokens, but that expressivity is not
actually used in the parser. Instead, we have `input.h` that adapts the token
iterator interface into an iterface that is actually useful.

As a first step toward simplifying the lexer implementation to no longer be an
iterator over tokens, update its interface by moving the adaptation from input.h
to the lexer itself. This requires extensive changes to the lexer unit tests,
which will not have to change further when we actually simplify the lexer
implementation.

0 files changed, 0 insertions, 0 deletions