add performance benchmarks

[MaxOstrowski]

Add a new option
nox -s performance
to run a currently 15min performance evaluation.
Doing this in different branches and then running
nox -s benchmark_compare -- .benchmarks/0001_xxx .benchmarks/0002_yyy
gives an overview of how the performance has changed between these versions

[AbdallahS]

@copilot please do the following changes:

• create a new file test_performance.py and move the new benchmark functionality introduced in this PR out of test_encoding.py to this new file.
• when I run nox and interrupt it with ctrl-c, I get the control back in my terminal but some benchmark tests are still being carried out in the background. Can you identify the reason for this behavior and fix it?