Fix pipenv --clear is not working

[jxltom]

The issue

Closes #3353

The fix

• pipenv --clear is supported by passing state.clear
• The exposed several values from click is removed from cli's arugment since options such as clear, python, three may be used in subcommands. It is better to access these values via state.
• Test is added

The checklist

• Associated issue
• A news fragment in the news/ directory to describe this fix with the extension .bugfix, .feature, .behavior, .doc. .vendor. or .trivial (this will appear in the release changelog). Use semantic line breaks and name the file after the issue number or the PR #.

[jxltom]

Oh, found a bug in vistir, submitted a PR sarugaku/vistir#47 fixing that in upstream. This PR should pass after vistir is vendored in pipenv.

[jxltom]

@techalchemy I think this PR is ready to merge since vistir is updated from upstream.

[jxltom]

Test for --three argument is added, test for --python has already existed in

pipenv/tests/integration/test_cli.py

Lines 33 to 37 in cae8d76

	@pytest.mark.cli
	def test_pipenv_py(PipenvInstance):
	with PipenvInstance() as p:
	c = p.pipenv('--python python')
	assert c.ok

.

[techalchemy]

for all the stuff that you're removing i'm assuming you have verified it still works?

[jxltom]

for all the stuff that you're removing i'm assuming you have verified it still works?

yep :D