Directly subclassing Iterable is lazy-ish, but if you call any operation
on the resulting value (eg. map or ++) it will evaluate the Iterable and
return a List.

This will make it easier to compile circuits with
older compiler versions.

* [smem] fix read-under-write serialization

Also adds some tests for the parser and
the serializer.

* Serializer: always serialize smem ruw behavior

* test: simplify smem test circuit

Also get rid of whitespace-only lines that were emitted after every when
block.

This is needed for emitting modules that serialize to Strings larger
than 2 GiB (the maximum String size on the JVM). It includes
micro-optimized logic for turning arbitrarily nested when scopes into
Iterable[String].

* Parse version and hardcode emitted version

* Throw error if version is too high

* Parse version even if rest is invalid

* Change pattern match to if statement

* Improve version grammar

* Update tests

* Remove outdated comment

* Simplify grammar and use version class

* Simplify and add no version test

* Fix for conflicting lexer rule

This will allow chiseltest to save
the hash code to disk for the purpose
of caching simulation binaries.