Feature tool-cache for Gleam and rebar3

[paulo-ferraz-oliveira]

Description

This pull request:

• in an attempt to ease maintenance...
  • gets rid of .ps1 and .sh files
  • moves all the content of src/installer.js into src/setup-beam.js
  • moves all the content of test/problem-matchers.test.js into test/setup-beam.test.js
  • centralises the mirror-iterating function in a single place, with a single interface (doWithMirrors)
  • while doing this we also ended up fixing an issue with not using mirrors for the Erlang/OTP build 👍
  • makes tool-cacheing -related behaviour callback -based (as explained in an extensive comment in the code)
  • improves debug logging
• has Gleam and Rebar3 use tool-cache as per the issue it closes
• is probably best reviewed commit by commit (given its size)
• basically leaves the tests untouched in an attempt to increase confidence on the changes ~ ⚠️ is not yet to be merged~ ~ I want to get #217 approved+merged so as to update this one (I'm sure there'll be merge conflicts)~

Closes #204.

• [x] I have performed a self-review of my changes
• [x] I have read and understood the contributing guidelines

Callback -based tool-cacheing -related behaviour

As an example, we show how Gleam is now configured for tool caching, on Linux (simplified here for illustration purposes):

downloadToolURL: () =>
  `https://github.com/gleam-lang/gleam/releases/download/${versionSpec}/gleam-${versionSpec}-x86_64-unknown-linux-musl.tar.gz`,
extract: async (file) =>
  ['dir', await tc.extractTar(file, undefined, ['zx'])],
postExtract: async () =>
  {},
reportVersion: () =>
  ['gleam', ['--version']]

[paulo-ferraz-oliveira]

Force-pushing to resolve conflicts. Flagging this as "Ready for review", too...

[paulo-ferraz-oliveira]

Rebased on top of main.

[paulo-ferraz-oliveira]

ping @starbelly