[Meta] Refactor lib\install.ps1

[Ash258]

This should be done when https://github.com/scoopinstaller/install is ready, so we do not have to care about moving something needed for scoop installation

1. Slim whole script
   1. Functions moving
      • There is no need to have every download / check function inside install module.
      • Install module should contain only install related functions
      1. nightly_version -> lib\versions.ps1
      2. Download related functions -> lib\download.ps1
         • dl_with_cache
         • do_dl
         • dl
         • dl_progress_output
         • dl_progress
         • dl_urls
      3. Aria2 related functions -> lib\aria2.ps1
         • aria_exit_code
         • get_filename_from_metalink
         • dl_with_cache_aria2
      4. Environment related functions -> lib\environment.ps1
         • env_add_path
         • add_first_in_path
         • env_rm_path
         • env_set
         • env_rm
      5. Persist related functions -> lib\persist.ps1
         • persist_def
         • persist_data
         • unlink_persist_data
         • persist_permission
      6. Extraction related functions -> lib\decompress.ps1 (decompress.ps1: Refactored (w/ install.ps1, core.ps1) (edited) #3169)
         • unpack_inno
         • extract_msi
         • extract_lessmsi
   2. Adopt Verb-Noun naming of functions
2. Downloading refactor / unify
   1. Download URl should strip scoop renames #/whaterever as it could potentially cause problems
   2. All dl_with_cache functions should have same parameter list
   3. There is incosistency between dl_with_cache normal and aria2 version
      • Aria2 version is capable of checking hashes
      • Aria2 version is removing cached file with $use_cache set to $false
      1. Create new function Initialize-Download ([String[]] $Url, [Switch] $UseCache, [Switch] $CheckHash)

         • This function will be only wraper, which will look like this:

           $paramsSplat = @{usecache, ...}
           if (aria2-enabled) { dl_witch_cache_aria2 @paramsSplat }
           elseif (curl-enabled) { dl_witch_cache_curl @paramsSplat } # Easier to maintain new download managers
           else { dl_witch_cache @paramsSplat }

         • This will save some lines, where you check for aria2 enabled in updates, install etc, ...

           • No need to manually check inside other code fractions. (as in [Workaround] Download and verify before update #3148)
           • You just call Scoop-Download and not care for anything

         • This wrapper will be called for dowloading instead of dl

         • Also it will allow binaries to use prefered manager without touching binary for each new download manager with some if

3. install_app function refactor
   • This should be enough to change https://github.com/lukesampson/scoop/blob/26d694e46dc973d97f404545f8627770daf4b35f/lib/install.ps1#L43 to 2 lines
     • Download (It could return $fname)
     • Extract if applicable
4. Adopt new download function in whole codebase (binaries, etc..)