Browser starts in about 1 to 2 seconds in a new sandbox

The browser now comes ready on the sandbox's host instead of being downloaded and installed on its first start, which took up to a minute: browser.start() in a brand-new sandbox now returns in about 1 to 2 seconds. A custom image that is not Ubuntu 24.04 x86_64 still installs it once on its first start (withruntime 0.17.2, and 0.16.1 for Python). See A browser over CDP.