Support defining global env vars in a config and using complex aliases.

[MHendricks]

To replicate the bug, add this environment section to tests/configs/app/app_aliased_mod.json

    "environment": {
        "set" : {
            "CONFIG_DEFINED": "config_variable"
        }
    }

Then when running this hab command, an KeyError: 'environment' error is raised.

$ hab -v dump app/aliased/mod
INFO:hab.cli:Context: app/aliased/mod
INFO:hab.solvers:Resolving requirements: {'aliased': <Requirement('aliased')>, 'aliased_mod': <Requirement('aliased_mod')>}
INFO:hab.solvers:Attempt 1 at resolving requirements
Hab encountered an error:
Traceback (most recent call last):
  File "C:\Program Files\Python39\lib\runpy.py", line 197, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "C:\Program Files\Python39\lib\runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File "C:\blur\dev\hab_\hab\__main__.py", line 14, in <module>
    sys.exit(hab.cli.cli(prog_name="python -m hab"))
  File "C:\blur\dev\hab_\hab\cli.py", line 496, in cli
    return _cli(*args, **kwargs)
  File "C:\Program Files\Python39\lib\site-packages\click\core.py", line 1130, in __call__
    return self.main(*args, **kwargs)
  File "C:\Program Files\Python39\lib\site-packages\click\core.py", line 1055, in main
    rv = self.invoke(ctx)
  File "C:\Program Files\Python39\lib\site-packages\click\core.py", line 1657, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "C:\Program Files\Python39\lib\site-packages\click\core.py", line 1404, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "C:\Program Files\Python39\lib\site-packages\click\core.py", line 760, in invoke
    return __callback(*args, **kwargs)
  File "C:\Program Files\Python39\lib\site-packages\click\decorators.py", line 38, in new_func
    return f(get_current_context().obj, *args, **kwargs)
  File "C:\blur\dev\hab_\hab\cli.py", line 415, in dump
    ret = settings.resolver.resolve(uri)
  File "C:\blur\dev\hab_\hab\__init__.py", line 270, in resolve
    return context.reduced(self, uri=uri)
  File "C:\blur\dev\hab_\hab\parsers\hab_base.py", line 489, in reduced
    return FlatConfig(self, resolver, uri=uri)
  File "C:\blur\dev\hab_\hab\parsers\flat_config.py", line 28, in __init__
    self._finalize_values()
  File "C:\blur\dev\hab_\hab\parsers\flat_config.py", line 71, in _finalize_values
    for platform, alias, data in self._process_version(
  File "C:\blur\dev\hab_\hab\parsers\flat_config.py", line 132, in _process_version
    global_env = self.frozen_data["environment"].get(host_platform, {})
KeyError: 'environment'

Checklist

• I have read the CONTRIBUTING.md document
• I formatted my changes with black
• I linted my changes with flake8
• I have added documentation regarding my changes where necessary
• Any pre-existing tests continue to pass
• Additional tests were made covering my changes

Types of Changes

• Bugfix (change that fixes an issue)
• New Feature (change that adds functionality)
• Documentation Update (if none of the other choices apply)

Proposed Changes

This MR forces the population of frozen_data["environment"] at the correct time so it can be when processing complex aliases.

[ghost]

Reviewed