add new setting to setting terminal startLocation

[krishnakanumuri]

PR Summary

This PR introduces a new integrated terminal setting to allow users to choose default start location based on their preference. This new setting allows user to set the Start Location for integrated terminal to either Edior or Panel.

When set to:

• Editor : Extension terminal starts in VS Code Editor area (current behaviour), this is the default.
• Panel : Extension terminal starts in VS Code terminal area (new behaviour)

This is realted to issue: #4181

PR Checklist

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• PR has a meaningful title
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[krishnakanumuri]

@microsoft-github-policy-service agree

[andyleejordan]

Oops. Sorry @krishankanumuri I accidentally pushed the wrong commit when editing your PR and closed this which now means I can't push to that branch again. Don't worry about it, I'll re-open a PR with your name on the commit.