feat(install/download-hosts): allow multiple per browser (#2452)
feat(install/download-hosts): allow multiple per browser (#2452)

In addition to `PLAYWRIGHT_DOWNLOAD_HOST` env variable, this patch adds a per-browser 
configuration:

- `PLAYWRIGHT_CHROMIUM_DOWNLOAD_HOST`
- `PLAYWRIGHT_FIREFOX_DOWNLOAD_HOST`
- `PLAYWRIGHT_WEBKIT_DOWNLOAD_HOST`
microsoft/playwright,microsoft/playwright,microsoft/playwright,microsoft/playwright,microsoft/playwright,microsoft/playwright,microsoft/playwright,microsoft/playwright,microsoft/playwright