Add JsonNode construction benchmarks

[eiriktsarpalis]

Contributes to dotnet/runtime#107869

[LoopedBard3]

I think this is a good start, although we will probably want to put the super fast benchmarks (<100ns per iteration) into a loop or something to get their mean time closer to 200-300ns in order to help minimize noisiness. If you have an idea of how to do this while keeping the tests inline with their goal and can make the change, that would be great, otherwise doing this exercise is one of the items we want to do.

[LoopedBard3]

@eiriktsarpalis Left a comment and approved the PR, whether you include the change mentioned in the approval, ping me when you are ready for this to be merged and I can merge it.

[eiriktsarpalis]

Something like 26e65c2?

[LoopedBard3]

Yes, exactly like that 👍. Thanks! Just to double check, are you good having this merged once the tests run?

[eiriktsarpalis]

Yep, go for it!

[LoopedBard3]

ubuntu Micro failure is related to a cryptographic error, not to any changes in this PR. Merging.