Testing: UI tests fail with device set to certain languages

[rachelmcr]

While generating app store screenshots for #15010, I realized it fails entirely (no screenshots generated on any device) when the device is set to th and ru. The test runs fail with this error:

testGenerateScreenshots, Failed to synthesize event: Timed out while synthesizing event.
LoginUsernamePasswordScreen.swift:41

However, the failures aren't specific to that PR and likely affect login for all of our UI tests in those languages.

[rachelmcr]

For some reason, English text entry fails in the password (secure text entry) field with Russian (ru) and Thai (th) keyboards, even though it works fine in other text fields.

One possible way to bypass this is to paste the text instead of typing it into the field, e.g. with an XCUIElement extension like this:

func pasteText(_ text: String) -> Void {
    UIPasteboard.general.string = text
    self.press(forDuration: 1.2)
    XCUIApplication().menuItems.element(boundBy: 0).tap()
}

I've found pasting like that to be a little flaky in past attempts, so I'm hesitant to rely on it. This looks like the most promising option I've found so far, though, so I'm going to try it out while generating a full set of screenshots and see how reliable it is across all those test runs.

I also looked into setting the keyboard language separate from the device language, but I haven't found a good way to do this programmatically just for testing. You can set it manually in your simulator settings (I/O > Keyboard > Use the Same Keyboard Language as macOS) but resetting the simulator also resets that setting.