Bug 1806465 [wpt PR 38609] - [Gecko Bug 1806465] [wdspec] Add add_preload_script...

Bug 1806465 [wpt PR 38609] - [Gecko Bug 1806465] [wdspec] Add add_preload_script and remove_preload_script commands to test client., a=testonly

Automatic update from web-platform-tests
[wdspec] Add add_preload_script and remove_preload_script commands to test client.

Depends on D169421

Differential Revision: https://phabricator.services.mozilla.com/D169422

bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1806465
gecko-commit: 394a052d0d01bc370fb4d4f112fd4ccd3d97fc06
gecko-reviewers: webdriver-reviewers, jdescottes

--
[wdspec] Add add_preload_script fixture to automatically remove preload script at the end of a test.

Depends on D169422

Differential Revision: https://phabricator.services.mozilla.com/D169423

bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1806465
gecko-commit: fb3bf839d51a97eaf966ff07b5c27856a5983b44
gecko-reviewers: webdriver-reviewers, jdescottes

--
[wdspec] Add tests for "script.addPreloadScript" and "script.removePreloadScript" commands.

Depends on D169423

Differential Revision: https://phabricator.services.mozilla.com/D169424

bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1806465
gecko-commit: c03f632f18cab66586557b77cc855675723753b5
gecko-reviewers: webdriver-reviewers, jdescottes

--
Fix remove_preload_script command return type.

--

wpt-commits: c2f34a0af3d9fe8a968db2d31cab971a7f5d4d26, ab76e1ff3de93c3466b8235b9882b973d519d218, 6d3b82daf2ecde1df78c2cfc9b15284e33422115, 3783e82d21df557df9b2b8db717ea6cb516bcda4
wpt-pr: 38609