Refactor pyexec (#1318)

This is some refactoring I did on the way towards resolving pyscript#1313.
I added a new _run_pyscript Python function which executes the code
inside a context manager that sets the display target. We can then
return a JS object wrapper directly from Python.

I moved the "installation" of the pyscript module to loadInterpreter,
and pyimport pyscript_py there and give it a type. This avoids a bunch
of creating and deleting of proxies for pyscript_py and allows us to
give it a type once and for all.

I also did some minor logic cleanup in a few places.

pyscriptjs/tests/py-unit/conftest.py

@@ -6,10 +6,6 @@ import pytest
 
 pyscriptjs = Path(__file__).parents[2]
 
-import pytest  # noqa
-
-pyscriptjs = Path(__file__).parents[2]
-
 # add pyscript folder to path
 python_source = pyscriptjs / "src" / "python"
 sys.path.append(str(python_source))
@@ -18,6 +14,7 @@ sys.path.append(str(python_source))
 python_plugins_source = pyscriptjs / "src" / "plugins" / "python"
 sys.path.append(str(python_plugins_source))
 
+
 # patch pyscript module where needed
 import pyscript  # noqa: E402
 import pyscript_plugins_tester as ppt  # noqa: E402

pyscriptjs/tests/py-unit/micropip.py

@@ -1,4 +0,0 @@
-"""Mock module that emulates some of the pyodide js module features for the sake of tests"""
-from unittest.mock import Mock
-
-install = Mock()

pyscriptjs/tests/py-unit/pyodide/ffi.py

@@ -1,4 +0,0 @@
-"""Mock module that emulates some of the pyodide js module features for the sake of tests"""
-from unittest.mock import Mock
-
-create_proxy = Mock(side_effect=lambda x: x)

pyscriptjs/tests/py-unit/pyodide/pyodide.py

@@ -1,4 +0,0 @@
-"""Mock module that emulates some of the pyodide js module features for the sake of tests"""
-from unittest.mock import Mock
-
-create_proxy = Mock(side_effect=lambda x: x)