* The header + expr fuzzers can both be run again (header fuzzer had regressed).
* I ran the expr fuzzer for ~60 seconds with no additional panics uncovered
* "tab_crash" hit supposedly unreachable code in blankspace.rs - and I went to the liberty of dramatically simplifying all that code, rather than just trying to fix the bug
* Other failures were straight-forward error cases that should have been handled (and passed up the chain) instead of panicking
As previously discovered with #4464, it's easy to accidentally mis-use the State value returned on the Err path.
There were mixed assumptions about what that State represents: (1) the State where the error occurred, or (2) the State at the beginning of the thing we were just parsing.
I fixed this up to always mean (2) - at which point we don't actually need to return the State at all - so it's impossible for further discrepency to creep in.
I also took the liberty to refactor a few more methods to be purely combinator-based, rather than calling `parse` directly.
Prior to this commit, if you had a module structure like
```
| - A.roc
| - Dep
| - B.roc
```
where `B.roc` was defined as
```
interface B exposes [] imports []
```
and `A.roc` was defined as
```
interface A exposes [] imports [Dep.B]
```
The compiler would hang on you. The reason is that even though we expect
`B` to be named `Dep.B` relative to `A`, that would not be enforced.
With this patch, we now enforce such naming schemes - a module must have
the namespaced name it is referenced by. Currently, we determine the
expected namespaced name by looking at how transitive dependencies of the
root module reference the module. In the future, once we have a package
ecosystem and a solid idea of "package roots", we can use the "package
root" to determine how a module should be named.
Closes#4094
