[Medium] Reimplement 'volta install' using global package install

[charlespierce]

Info

• First step of the package rework: Install packages using npm install --global with a redirect into a Volta-managed directory.
• Install into a temporary directory first, to avoid creating unnecessary directories in the event of an error.
• This PR explicitly doesn't include parsing the package.json or writing configs & shims, those will be added in a future PR.

Changes

• Added new error messages for new error paths.
• Created global_install method to actually run the install command.
• Created skeleton implementation of Tool::install for Package
• Included TODO comments for areas that will be added in future PRs.

Tested

All tested locally as automated tests will be added in a future PR, when the entire workflow is complete

• Confirmed packages are installed and executable in the expected location.
• Verified that the issue described in Cannot find module when sub-package depends on the root package #762 is resolved (since the directory structure includes node_modules)
• Ensured directories aren't created when there is an error with installation (e.g. when the package doesn't exist)

Notes

• volta fetch <package> was made into an error because with the switch to using npm install --global directly it doesn't work the way it would be expected to.
  • Since the install process is entirely managed by npm, we can't reasonably have a "pre-fetched" version around to shortcut.
  • If we allowed it, the volta install <package> process would ultimately overwrite it anyway, because we would need to ensure that we were using the potentially new Node version.

[chriskrycho]

Looks good! I had a couple questions, but wholly for my own learning!