Update to LTS and above versions of Julia

[ven-k]

• Fixes the package for Julia-1.8 and above
• The Pkg#release-1.8 has dropped the function from PlatformEngines.jl
• It "didn't do anything" even in release-1.7 (see here)
• Perhaps this function can be dropped here as well
  - Depends on ci: Bump FreeBSD image version to 13 #212 for CI to run

[ven-k]

I've expanded scope of the PR to make it work on Julia LTS and above.

The package seemed to need these updates additionally:

• Use Platform to define the platform values (instead of Linux, Windows, MacOS)
• (Because of above reason) Update the lower bound of Julia to v1.6
• Fix platform check condition in locate
• Define list_tarball_files: This function is moved to tests\Utils in Pkg.PlatformEngines
• Use unpack alternative: unpack function internally uses Tar.extract which requires destination dir to be emptyunpack function internally uses Tar.extract which requires destination dir to be empty

There still seem to be few test failures. In "Packaging", certain exceptions aren't raised. In "Libfoo downloading", isinstalled returns false, even when the path exists.