Move pyodide to a web worker (#1333)

This PR adds support for optionally running pyodide in a web worker:

- add a new option config.execution_thread, which can be `main` or `worker`. The default is `main`

- improve the test machinery so that we run all tests twice, once for `main` and once for `worker`

- add a new esbuild target which builds the code for the worker

The support for workers is not complete and many features are still missing: there are 71 tests which are marked as `@skip_worker`, but we can fix them in subsequent PRs.

The vast majority of tests fail because js.document is unavailable: for it to run transparently, we need the "auto-syncify" feature of synclink.


Co-authored-by: Hood Chatham <roberthoodchatham@gmail.com>
Co-authored-by: Madhur Tandon <20173739+madhur-tandon@users.noreply.github.com>

pyscriptjs/tests/integration/test_stdio_handling.py

@@ -1,4 +1,4 @@
-from .support import PyScriptTest
+from .support import PyScriptTest, skip_worker
 
 
 class TestOutputHandling(PyScriptTest):
@@ -183,6 +183,7 @@ class TestOutputHandling(PyScriptTest):
 
         self.assert_no_banners()
 
+    @skip_worker("FIXME: js.document")
     def test_targeted_stdio_dynamic_tags(self):
         # Test that creating py-script tags via Python still leaves
         # stdio targets working
@@ -292,6 +293,7 @@ class TestOutputHandling(PyScriptTest):
         assert self.page.locator("#stderr-div").text_content() == "one."
         self.assert_no_banners()
 
+    @skip_worker("FIXME: js.document")
     def test_stdio_output_attribute_change(self):
         # If the user changes the 'output' attribute of a <py-script> tag mid-execution,
         # Output should no longer go to the selected div and a warning should appear
@@ -325,6 +327,7 @@ class TestOutputHandling(PyScriptTest):
         alert_banner = self.page.locator(".alert-banner")
         assert expected_alert_banner_msg in alert_banner.inner_text()
 
+    @skip_worker("FIXME: js.document")
     def test_stdio_target_element_id_change(self):
         # If the user changes the ID of the targeted DOM element mid-execution,
         # Output should no longer go to the selected element and a warning should appear