When looking at where we spend our time in solver setup, I noticed a fair bit of time is spent
in `Spec.format()`, and `Spec.format()` is a pretty old, slow, convoluted method.
This PR does a number of things:
- [x] Consolidate most of what was being done manually with a character loop and several
regexes into a single regex.
- [x] Precompile regexes where we keep them
- [x] Remove the `transform=` argument to `Spec.format()` which was only used in one
place in the code (modules) to uppercase env var names, but added a lot of complexity
- [x] Avoid escaping and colorizing specs unless necessary
- [x] Refactor a lot of the colorization logic to avoid unnecessary object construction
- [x] Add type hints and remove some spots in the code where we were using nonexistent
arguments to `format()`.
- [x] Add trivial cases to `__str__` in `VariantMap` and `VersionList` to avoid sorting
- [x] Avoid calling `isinstance()` in the main loop of `Spec.format()`
- [x] Don't bother constructing a `string` representation for the result of `_prev_version`
as it is only used for comparisons.
In my timings (on all the specs formatted in a solve of `hdf5`), this is over 2.67x faster than the
original `format()`, and it seems to reduce setup time by around a second (for `hdf5`).
aa0825d642