add definition of 'COMMON_TEST' macro to eunit provider

This patch adds support for short options in the eunit provider.

this ONLY attempts to deduplicate test sets that are generated by
rebar in the absence of any user specified tests

`beam_lib:chunks(..)` needs a path to object code which, frustratingly,
`code:which/1` won't return for cover compiled modules. instead just
assume that if `code:which/1` doesn't return `non_existing` a module
is something we can run tests on

into directory test arguments

The previous default meant that verbose output would not be emitted.

when `ct_opts`, `eunit_tests`, `eunit_first_files`, `ct_first_files`, `erl_first_files`,
`eunit_compile_opts`, `ct_compile_opts` and `erl_opts` have values that are single non-list
terms warn and try wrapping them in a list when processing them in the `eunit` and `ct`
providers

at the cost of some SASL warnings this prevents rebar3 from terminating
processes when reloading their code before running tests

* 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

prior to running compile and compile prehooks

This reverts commit dde60d491f.

profiles are for

This reverts commit b06a6ecadd.

- Crashes in providers lib when no providers in a namespace are bare
- Making sure bareness matches semantics; i.e. a bare provider is
  visible, a non-bare provider is hidden.

adding it results in ct test suites being compiled before they're
properly copied so changes made to suites between runs are not
reflected if a run fails before test dirs are copied

like `src_dirs`, `extra_src_dirs` are directories to be copied to
the `_build` dir and compiled. unlike `src_dirs` they are not added
to the .app specification

matching directory paths

run subsets of test suites

Also expose it in rebar_api

root project

get correct compile paths included in module info