* modify compiler interface to work on either application objects or
  directories containing source files
* compile all sources in `src_dirs` to the application `ebin` dir and
  all sources in `extra_src_dirs` to a directory mirroring it's
  position in the app's `_build` directory. for example, `apps/foo/more`
  would compile to `_build/default/lib/foo/more`
  for `extra_src_dirs` in the root of a project with multiple
  applications (so orphan directories that don't "belong" to an
  application) compile to `_build/default/extras/more`
* copy directories specified in `extra_src_dirs` into the `_build`
  directory so tools like `ct` and `xref` that expect source to be
  in a particular location still work
* clean compiled artifacts from all `extra_src_dirs`
* alter `eunit`, `ct` and `cover` to work with the new directory
  structure
* billions of new tests

This reverts commit 9d82215296.

This passes the directory to the option to ensure it works with more
than configs at the root of the project.

prior to running compile and compile prehooks

This commit replaces the method of upgrading by unlocking all transitive
deps by one that utilizes the parent element of each app to only
unlock transitive deps of children of the top level deps being upgraded.

Additionally the run function of upgrade_SUITE is modified to only create
the mock updates before the upgrade provider is run, instead of before
any provider is run, which would cause improper behavior in install_deps.

to `rebar_erlc_compiler`

`reduce_path/1` -> `canonical_path/1`
`relative_path/2` -> `path_from_ancestor/2`

this test almost certainly only fails under very limited circumstances
limiting it's utility. it is known to fail with some versions of rebar3
when this test is run via `rebar3 ct --cover`

add tests

Instead fetching and resolving src deps (which could depend on pkg deps)
and then pkg deps this patch combines the two into a single set of
iterations by level. The only difference between src and pkg deps in this
new install_deps is how their deps list is found -- from the config or
lock file for src deps and from the neighbors of the vertex for pkg.

Just rework the error message.

On a single app's dep list, the first noted wins if there's a duplicate
between packages and sources, rather than favoring source there anyway.

Requires a rework of other test suites using the same dep-handling
mechanism.