fix: Place `.playwright` directory under bin directory

[filzrev]

This PR intended to fix issue #10398. By temporary revert commit (https://github.com/dotnet/docfx/pull/9363)

Background When using PLAYWRIGHT_NODEJS_PATH environment variable. ../../.playwright fallback from bin directory is not used. And failed to find .playwright\package\cli.js file.

• https://github.com/microsoft/playwright-dotnet/blob/main/src/Playwright/Helpers/Driver.cs#L89-L90
• https://github.com/microsoft/playwright-dotnet/blob/main/src/Playwright/Helpers/Driver.cs#L145

To fix problems. it need to change playwright-dotnet side code
(or install chromium browser directly by calling .playwright/package/cli.js)

So I've temporary reverted #9363 code. And place .playwright folder under bin directory. By this changes. .nupkg size increased about 1.8MB.