Added buffering to prevent heavy logging issues

[gcampbell-msft]

• Adding buffering to help the output window handle heavy amounts of output
• This PR will solve various issues that have been reported: Serial Monitor no output #1402 Serial monitor can't handle large amounts of data #1410 Serial Monitor not updating in real time #1396

Side effect of implementation of this fix:

• Removed the need for the serialportctrl to hold a reference to the vscode.OutputChannel in order to call the show() method. Replaced this with a method callback that can be passed to the constructor.

[benmcmorran]

Retargeting this PR to main.

[benmcmorran]

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