Add support for network experiments

This commit adds support for network experiments on our status page
without the incident language.

In particular, it

1) creates a new layout (experiments),
2) overwrites the default components page to take network experiment
   differences into account,
3) adds a Network Experiments item to the Tor Network section.

Note: this commit has a dependency on a cstate commit providing the new
strings to use.
1 job for network-experiments in 13 seconds (queued for 1 second)
Status Name Job ID Coverage
passed test #22190