Bug 40035: Added a fonts fingerprinting test

Added a test to check that fingerprinting can only detect the fonts we bundle with Tor Browser. The code is readapted from TorZilla Print: https://arkenfox.github.io/TZP/tests/fontlists.html

The list should be updated to match the bundled fonts. Also, we ship different fonts in different platforms, so the test is enabled only for Linux.

Added also a test to detect which glyph the browser can render and their size. The code was originally developed by David Fifield and Serge Egelman: https://www.bamsoftware.com/talks/fc15-fontfp/fontfp.html#demo

The expected result of the test comes directly from a run on Tor Browser, and we want it to be persistent, rather than having some deisred metrics to match.

Fixes #40035 (closed).