plugin: Support LogOutputChannel

[ndoschek]

What it does

• Support LogOutputChannel
• Support LogLevel
• Support in namespace/env: logLevel & onDidChangeLogLevel

Resolves eclipse-theia#12017

Contributed on behalf of STMicroelectronics.

Remark:

This PR contributes the basic VS Code API support for LogOutputChannels, to fully support all aspects of a LogOutputViewChannel as in VS Code some additional features will be needed:

• In VSCode there is support to set the "Developer log level" in the application which also configures the log level for LogOutputviewChannels. Currently the log level for LogOutputChannels is set to the default log level, i.e. info.
• VSCode also writes the logs to a separate file per extension and offers a command and tool in the output view to directly open the extensions's log file.

I suggest to extract those additional features into separate follow-up issues if you agree.

How to test

To test, I created a simple extension that creates a LogOutputChannel and contributes commands to send log messages in different levels:
vscode-extension-log-output-channel-12017-0.0.1.zip

1. Download and install the test extension vscode-extension-log-output-channel-12017-0.0.1.vsix in your Theia test workspace (via Extensions view - top menu bar More actions... - Install from VSIX).
2. On activation of the extension, the log output channel LogOutputChannel-Test-12017 is shown in the output view and the initial message (LogLevel set to: Info) should be shown.
3. Execute the commands (Log a <loglevel> message via LogOutputChannel) via the command palette and check for the messages in the output channel.
   Remark: Currently the loglevel is set to default INFO log level.

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

[rschnekenbu]

Thanks, that looks good to me!
I tested also to change the loglevel in packages/plugin-ext/src/plugin/output-channel/logoutput-channel.ts to trace and I could get a log for all levels.

[ndoschek]

Thank you @rschnekenbu! Closing this in favour of eclipse-theia#12429