Apply version ranges to nuspecs during fix-up command - #3835

Per #2883, version ranges specified in paket.dependencies weren't patched into auto-generated nuspecs as part of the fix-nuspecs call. This PR attempts to add them in, in addition to a slight cleanup of the existing logic to make it easier to follow in my view.

The approach is to first determine what the nuspec file ranges should be for all known dependencies. This is done by taking the ranges specified in the dependencies file, which are optimistic, and modifying them with the 'resolved' information from the lock file. What this means depends on the type of range specified:

• for greater than, minimums, specific versions and overrides, this means changing the semver used for that bound to be the locked version. This seems safe for every case.
• for maximums, this means changing the range to a Between, because we want to ensure that consumers use at least the version that this package was built against, while not going higher than this package's own build requirements
• similarly for less than, we want to ensure that the minimum bound is changed to the version that this package was built against
• finally for Ranges, we change the lower bound to an inclusive lower bound on the locked version for similar reasons.

Once we have these ranges derived, we iterate through the dependencies in the nuspec as before, only taking action if we encounter a dependency that we know is a direct dependency.

Caveats:

• this only tracks the main group of dependencies
  • we have the references file for this project, we could use that information to look for the range of the group that was actually referenced.
• this does not take into account targetframework restrictions.

I don't have tests for this yet, but from manual testing on F# Formatting (after adding an upper bound myself to the dependencies file and manually calling fix-nuspecs on the generated nuspecs), this seems to work:

nuget FSharp.Compiler.Service >= 35.0 < 36.0 lowest_matching:true

results in a nuspec with the range

<dependency id="FSharp.Compiler.Service" version="[35.0.0,36.0.0)" exclude="Build,Analyzers" />