Fixes the issue of the test using braced parameter expansion, which is
not part of Shell's syntax, and correctaly sets up the test directory,
ensuring its path is fully resolved to avoid issues on macOS.
This change ensures that users can use LibShell easily understand this
library now, because we have an actual library directory.
In addition to that, we move the test scripts to Tests/LibShell, to
match the usual pattern of putting test-related files in the Tests/
directory.
Eduardo Casadei