Allow somewhat fuzzy version matching for install and uninstall commands

[interstateone]

This PR extracts the behaviour added in #115, which allows users to omit prerelease identifiers (like "beta 2") in command arguments when it's unambiguous, and uses it in the install and uninstall commands. If the version is ambiguous then it should fail.

Testing

First, clone this repo if necessary and check out the PR branch:

git clone https://github.com/RobotsAndPencils/xcodes.git
cd xcodes
git checkout -b interstateone-116-fuzzy-install-uninstall master
git pull https://github.com/interstateone/xcodes.git 116-fuzzy-install-uninstall

Right now there's a 12.3 beta available, and with this change you should be able to install it without specifying the beta identifier:

swift run xcodes update
swift run xcodes install 12.3

The tests that were added provide examples of how this should work in other situations, and you can try out the install and uninstall commands to verify. If there's an exact match even if there are multiple possible matches (like 12.2, when 12.2, 12.2 beta 1, 12.2 beta 2, 12.2 beta 3, and 12.2 release candidate are available) then it'll match 12.2. Once the next 12.3 beta is released then 12.3 is no longer unambiguous and would fail to match.

Closes #116.

[thii]

Thanks for this.

[senmu]

Code changes look great and thanks for the easy to follow testing instructions. Installing the 12.3 beta using fuzzy matching worked for me.