…g common syntax forms, and they are all passing. The biggest thing that's missing right now is handling Solidity's specific semver quirks and edge cases, which are definitely not handled.

…nts of a Solidity source file as input and shallowly parses it to pull out any version pragmas. It thencompares all of the pragmas to the full list of available versions and returns a list of all the versions which pass.

…urce files against the actual version used to compile them according to Sanctuary. I'm marking two kinds of version errors here: one for when we can't infer a version from a source file, and one for when the actual version is not included in the inferred versions list.

…d of Sanctuary testing.

At first this was extacting the version pragmas by just going line-by-line and finding lines that start with `pragma solidity`. This is obviously an overly simplistic way to do this. One glaring issue here is that if a source file has a version pragma inside a block comment, then that would still be included in the list of pragmas that must be matched.

This update uses slang's parser instead to extract all of the real version pragmas, and then the custom semver parser to do the rest. After making this change we have 0 version inference errors from Sanctuary.

…ators (`^` and `~`) in hyphen ranges. These two things don't make sense to be included together, and most likely a correct parser would fail to parse this range. However, Solidity does/has just ignored these operators in the case of a hyphen range, so we will do that too.

I copied the semver parsing/matching test cases from solc and recreated them here. From there I fixed any weird behaviors that weren't already handled. Most importantly, solc allows users to specify operators in front of partial version ranges, which leads to some unintuitive behavior.

…rly in some circumstances

* Refactored the parser code to move the types and base implementations to `semver/mod.rs`, and all the parsing code in `semver/parser.rs`.

…ype of thing is getting parsed. Also trying to simplify/consolidate some of the higher-level parsing bits.

* Add `has_known_version_mismatch` check to the sanctuary tests so that we skip files where the version in sanctuary is known to not match the version pragmas

… our purposes they're interchangable, all of the custom semver parsing/handling happens in `PartialVersion`, `Comparator`, and `ComparatorSet` - once we reduce the versions to concrete versions then we don't need anything special. This results in a bit less custom code.

…he custom `VersionIterator`

…nge`

Co-authored-by: Omar Tawfik <15987992+OmarTawfik@users.noreply.github.com>