Drop `Exercises` from the module name

[waseem-medhat]

Module names are kinda unwieldy (e.g., one function call looks like this Spirit.Exercises.BinariesStringsAndCharlists.describe_string(s)). So, I suggest we update our structure to mitigate this by replacing the directory name from exercises to just spirit. I've shown it in detail below to make it clear.

Directory structure:

• Before: lib/exercises/binaries_strings_and_charlists.ex
• After: lib/spirit/binaries_strings_and_charlists.ex

Module name:

• Before: Spirit.Exercises.BinariesStringsAndCharlists
• After: Spirit.BinariesStringsAndCharlists

An added bonus is that this structure is probably more idiomatic since LSP completion now detects the module name correctly when I use the defmodule snippet.

[nikfp]

I agree that this makes more sense overall. And since having it work with existing tooling is one of our primary goals I think this chance makes sense from an LSP standpoint as well.