Forward webview console log messages to browser console

[tortmayr]

What it does

This ensures that webview console logs are correctly propagated to the backend logger.
Webview are rendered inside of an IFrame this means console logs are isolated and are not forwarded to the backend logger
(in contrast to console logs of the main frontend process).

This change extends the default script injected into webviews to override the global console and send a log message via the postMessage API instead. This event is than handled by the `Webview´ base class and forwarded to the browser console.
In addition to forwarding to the backend logger this also makes it easier to identify log messages that are coming from webviews as they are now prefixed with [webview: ]

Contributed on behalf of STMicroelectronics

How to test

This can be tested with any vsocde-extension that provides a webview with console logs.
I used the CatCoding webview sample and added the following console logs to the webview main script:

    console.log("Test extension webview  is ready!")
    console.debug("Debug test message")
    console.error("Error test message")
    console.warn("Warn test message")
    console.info("Info test message")
    console.trace("Trace test message")
    const foo=()=>{console.log("foo")};
    console.log("Function foo",foo);

The vsix for this customized cat coder can be found here:
cat-coding-0.0.1.zip

To test, add it to the plugin folder,
open the Theia application and then use the Cat Coding: Start coding session command to open the webview.

Expected result: The console logs mentioned above should show up in the browser console and the backend console.

Follow-ups

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• As a reviewer, I agree to behave in accordance with the review guidelines

[msujew]

Works great, thanks!

I have a formatting related comment, but everything else looks good 👍

[tortmayr]

@msujew Thanks for the fast review. I have (hopefully) fixed the mentioned formatting issues. Also I made sure to remove any indentation overhead at the beginning of each line (as template strings preserver whitespaces).