Tidy up benchmarks

There are several things we need to fix.

Since go 1.24 pereferable way to write benchmarks is to use b.Loop. We have a lot of benchmark functions which use b.N and some of them rely on b.N value which is incorrect.

Some benchmarks are just useless (take a look at node.BenchmarkCopy). We need to get rid of such benchmarks. Not just because they are useless but also some of them take a lot of time to execute (they are too fast and it takes time for testing package to figure out number of iterations to reach duration of 1 second).

Some of benchmarks are incorrect. For example, node.BenchmarkOr. Node size depends on b.N and therefore (on some laptops) such benchmarks never converge. Here is article by Dave Cheney (https://dave.cheney.net/2013/06/30/how-to-write-benchmarks-in-go) - take a look at Traps for young players section. Also for some benchmarks (again node.BenchmarkCopy) compiler optimizes away all the code.

• use b.Loop everywhere;
• remove useless benchmarks;
• do not rely on b.N;