`useIncognitoPages` doesn't rotate fingerprints about crawlee

[barjin]

Seems like a sign of a much larger underlying issue:

New sessions / fingerprints / proxyUrls are generated only on a browser launch.

The following snippet doesn't rotate the fingerprints correctly - all requests are done with one session only. This is because the useIncognitoPages was written with Playwright contexts in mind - we relied on the "newPage() creates a separate environment" invariant, so all the pages/contexts are launched in one browser.

sessionPoolOptions: {
    sessionOptions: {
        maxUsageCount: 1,
    },
},
launchContext: {
   useIncognitoPages: true,
},

The following snippet rotates the fingerprints correctly:

sessionPoolOptions: {
    sessionOptions: {
        maxUsageCount: 1,
    },
},
launchContext: {
   useIncognitoPages: false,
},

This works well because an "expired" session throws away the whole browser instance, causing the new pages to launch a whole new browser (see the parallel with the maxOpenPagesPerBrowser, which does the same thing). This is crazy expensive though, while launching and closing a context 100 times in one browser takes ~3.9 seconds, launching and closing a browser 100 times takes 40 seconds.

The entire browser-pool and session rotation logic is quite convoluted and worth a total rewrite.