Cleanup internal API handling

[Rylan12]

This PR does a few cleanup things:

1. Removes references to HOMEBREW_USE_INTERNAL_API in Homebrew::API::{Formula,Cask}. This functionality will end up living in Homebrew::API::Internal (coming soon)
2. Move the formula_aliases.txt file generation to a helper method in Homebrew::API. This is only used in one place for now, but eventually will be used in Homebrew::API::Internal
3. Enable download queue support for individual formula/cask API fetches
4. Add alias, rename, and tap migration information to the internal API generation

A quick note on the last item: this means that the minimal JSON file now is in this format:

{
  "formulae": {
    "name": ["pkg_version", rebuild, "sha256"],
    ...
  },
  "aliases": {
    "alias_name": "real_name",
    ...
  },
  "renames": {
    "old_name": "real_name",
    ...
  },
  "tap_migrations": {
    "name": "tap",
    ...
  }
}

I tried a few different structures to see which was the most space-efficient when compressed, and this seemed to be the best and most readable. I'm happy to share these results if anyone is interested. Also happy to try other suggestions.

Here are the compressed file sizes:

$ eza -l
.rw-r--r-- 175k rylanpolster 10 Aug 23:31 formula.arm64_big_sur.json.gz
.rw-r--r-- 334k rylanpolster 10 Aug 23:31 formula.arm64_linux.json.gz
.rw-r--r-- 206k rylanpolster 10 Aug 23:31 formula.arm64_monterey.json.gz
.rw-r--r-- 376k rylanpolster 10 Aug 23:31 formula.arm64_sequoia.json.gz
.rw-r--r-- 376k rylanpolster 10 Aug 23:31 formula.arm64_sonoma.json.gz
.rw-r--r-- 376k rylanpolster 10 Aug 23:31 formula.arm64_tahoe.json.gz
.rw-r--r-- 376k rylanpolster 10 Aug 23:31 formula.arm64_ventura.json.gz
.rw-r--r-- 176k rylanpolster 10 Aug 23:31 formula.big_sur.json.gz
.rw-r--r-- 161k rylanpolster 10 Aug 23:31 formula.catalina.json.gz
.rw-r--r-- 126k rylanpolster 10 Aug 23:31 formula.el_capitan.json.gz
.rw-r--r-- 137k rylanpolster 10 Aug 23:31 formula.high_sierra.json.gz
.rw-r--r-- 147k rylanpolster 10 Aug 23:31 formula.mojave.json.gz
.rw-r--r-- 206k rylanpolster 10 Aug 23:31 formula.monterey.json.gz
.rw-r--r-- 377k rylanpolster 10 Aug 23:31 formula.sequoia.json.gz
.rw-r--r-- 129k rylanpolster 10 Aug 23:31 formula.sierra.json.gz
.rw-r--r-- 377k rylanpolster 10 Aug 23:31 formula.sonoma.json.gz
.rw-r--r-- 377k rylanpolster 10 Aug 23:31 formula.tahoe.json.gz
.rw-r--r-- 377k rylanpolster 10 Aug 23:31 formula.ventura.json.gz
.rw-r--r-- 377k rylanpolster 10 Aug 23:31 formula.x86_64_linux.json.gz

[MikeMcQuaid]

Looks great, thanks @Rylan12! Will merge after next release.