chore: remove bin dir and simplify tests.__main__ (#8507)

.dvcignore

@@ -1,4 +1,3 @@
 /tests
 /dvc
 /.github
-/bin

bin/dvc

@@ -1,3 +0,0 @@
-#!/bin/bash
-
-PYTHONPATH=$DVC_HOME python -m dvc $@

bin/dvc.bat

@@ -1,3 +0,0 @@
-@echo OFF
-set PYTHONPATH=%DVC_HOME%
-python -m dvc %*

tests/__main__.py

@@ -1,20 +1,6 @@
-# Needs investigation, pylint was running tests
-# Could be `pylint_pytest` plugin, skipping check for this file for now
-# pylint: skip-file
+if __name__ == "__main__":
+    import sys
 
-import os
-import sys
-from subprocess import check_call
+    import pytest
 
-REPO_ROOT = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
-os.chdir(REPO_ROOT)
-
-os.putenv(
-    "PATH", ":".join([os.path.join(REPO_ROOT, "bin"), os.getenv("PATH")])
-)
-os.putenv("DVC_HOME", REPO_ROOT)
-
-opts = "-v -n=auto --dist loadscope --cov=dvc --durations=50"
-params = " ".join(sys.argv[1:])
-cmd = f"{sys.executable} -m pytest {opts} {params}"
-check_call(cmd, shell=True)
+    sys.exit(pytest.main(["-v", "-n=auto", *sys.argv[1:]]))