dune-pkg: Improve error messages when source archive can't be extracted

[gridbugs]

Desired Behavior

When dune downloads a package source archive but is unable to extract it, the error message should help users solve the problem. One type of problem is if the necessary tool for extracting the archive (tar or unzip) isn't installed. It's also possible that tar can be installed but the decompression tool (often gunzip or bunzip2) is missing. There may be other helpful error messages that a tool would try to print that dune currently doesn't present to users, such as if there is not enough disk space to extract the archive.

Currently, dune will print the following in all cases of failing to extract an archive:

File "dune.lock/tsort.pkg", line 10, characters 7-65:
10 |   (url https://github.com/dmbaturin/ocaml-tsort/archive/2.0.0.zip)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Error:
failed to unpack archive downloaded from
https://github.com/dmbaturin/ocaml-tsort/archive/2.0.0.zip
reason:
unable to extract "_build/.temp/dune_d7c5e3_2.0.0.zip/download"

This example error was from attempting to extract a zip archive on a machine which does not have unzip installed. It would be helpful if dune presented that information to the user.

If the required tool is installed but the extraction still failed, it would be helpful if the stderr from the failed attempt to run the tool could be printed.

[create2000]

Hello @gridbugs . My name is Anthony Onah, an applicant for the Outreachy Internship. Can i have this issue assigned to me? Thanks

[AdmKing]

hello sir. I would like to fix this issue. @gridbugs

[bqcarima]

Hello @gridbugs. My name is Bassey Otudor an Outreachy internship applicant. I would like that you assign this issue to me.

[gridbugs]

Since this is such a popular issue, I'm going to split it into some sub issues so @create2000, @AdmKing and @bqcarima can all contribute here. I'll make some sub issues and let the 3 of you decide which one each will focus on.

[gridbugs]

Ok I've created 3 sub issues. Let me know which of you will be working on which issue and I'll assign you!