Improve function name logging during function tracking

[surovic]

In the current implementation fast path, each function entry would have to

1. strlen(function-name)
2. acquire lock
3. lookup function name map (compute hash)
4. return index

Couldn't all this information be known at compile time? I don't think we should change the current approach, but rather think about if we should do a follow up PR that tries to shift as much work as possible to compile time.

Originally posted by @hbrodin in #6473 (comment)