- Refactor the lexer tests to be more readable, abandoning the
previous string-based summary DSL in favor of a more obvious
sequence of `TokenKinds` with optional lexemes. The new tests
also test that token lexemes are correct.
- Move duplicated `unindent` function into a shared crate,
`test-utilities`. This new versionless dev-dependency will
prevent publishing to crates.io, at least until rust-lang/cargo/pull/7333
makes it into stable. If we publish a new version before then,
test-utilities will need to be published to crates.io, so we can depend
on it by version.
