switch to serious multi-byte testing

[zikaari]

No description provided.

[zikaari]

@aeschli any thoughts on including this in the next release?

[aeschli]

+1 for improving our benchmark. But I would suggest to add a new test instead of replacing the existing one.
Also I would suggest avoiding randomized inputs but use real-world examples.

• avoid random to make it reproducible
• avoid optimizing against inputs that are rare or net even existing.