[TODO] [PENDING #8635] renamed: compiler.nimble -> compiler/compiler.nimble

[timotheecour]

pending #8635 which introduces hierarchical modules, it now makes more sense to nest compiler.nimble so we have these:
CC: compiler.pragmas
instead of these:
CC: compiler.compiler.pragmas

pretty much everything else is like that (foo/foo.nimble instead of foo.nimble)

• TODO:address this failure:

the command "nim e tests/test_nimscript.nims" exited with 0.
$ nimble install zip -y
     Error: Incorrect .nimble file: /home/travis/build/nim-lang/Nim/nimroot.nimble does not contain a version field.

[GULPF]

Pretty sure that this change would mean that repo isn't a valid Nimble package anymore. Note that the compiler can currently be installed as a library using Nimble.

[dom96]

Nimble now supports packages which are not in the repo root, so this file could be moved.

The packages.json file just needs to be updated. Unfortunately this creates a problem: installing an older version of the compiler package will fail since it's going to look in the wrong place for the .nimble file :(