Record start url support

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Summary

• Adds a playwright.recordStartUrl VS Code setting that configures a URL to navigate to when using "Record new"
• When set, the generated test template includes await page.goto(url) which navigates the browser before recording starts
• Includes URL scheme validation (http://, https://, file://, etc.) with a localized error message
• When empty (default), behavior is unchanged — recording starts on about:blank

Motivation
Currently, clicking "Record new" opens the browser at about:blank and the user must manually navigate to their application. The CLI equivalent (playwright codegen ) supports a URL argument, but the VS Code extension had no equivalent. This setting closes that gap.

How it works
The URL is embedded as page.goto() in the generated test template. The test runs before recording starts, navigating the browser in-place — no subprocess or CDP manipulation needed.

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@microsoft-github-policy-service agree

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It also fixes issue 20059