Added tooling for trie stats

[BGluth]

A bit more tooling related to extracting stats from tries. Primary use case that I want from this is to compare sub-tries from the base trie they were created from.

To give an idea of what the output looks like:

Trie Stats: (local_partial_plus_delta_storage_txn_4.json)
Counts:
Empty: 39 (18.660%)
Hash: 154 (73.684%)
Branch: 13 (6.220%)
Extension: 0 (0.000%)
Leaf: 3 (1.435%)

Depth stats:
Lowest depth: 4
Average leaf depth: 4.000
Average hash depth: 2.604

Trie Stats: (local_full_post_delta_storage_txn_4.json)
Counts:
Empty: 50 (19.455%)
Hash: 164 (63.813%)
Branch: 16 (6.226%)
Extension: 0 (0.000%)
Leaf: 27 (10.506%)

Depth stats:
Lowest depth: 4
Average leaf depth: 4.000
Average hash depth: 2.433

Node comparison: Total nodes: 209 / 257 (81.323%)
Non-empty: 170 / 207 (82.126%)
Total empty: 39 / 50 (78.000%)
Total hash: 154 / 164 (93.902%)
Total branch: 13 / 16 (81.250%)
Total extension: 0 / 0 (NaN%)
Total leaf: 3 / 27 (11.111%)

Depth comparison: Lowest depth: 4 / 4 (100.000%)
Avg leaf depth: 4.000 / 4.000 (100.000%)
Avg hash depth: 2.604 / 2.433 (107.027%)

[muursh]

returning the state rather than using a mut state as an arg would be more rusty

[BGluth]

The only downside is then we would need to do more computation when merging together multiple CurrTrackingState together, which I guess doesn't really matter too much.

[BGluth]

Will revisit this afterwards!

[muursh]

Given it's just a debug tool I'm not too worried about the bits I noted. Having working tools is more useful than not.

[Nashtare]

Thanks @BGluth!
I'll stop commenting now because most of my comments are identical. So global points:

• we can probably not have pub most methods / objects lying around. I think that's probably good practice to reduce public API in general.
• we can add some clearer documentation on new types and methods, but it's not blocking.

[muursh]

I think that's probably good practice to reduce public API in general.

Yeah agreed. Meant to comment this.

[BGluth]

Hmm yeah. So I ended up making a lot more of the interface public at the last minute because I thought the callers might want to access the stat data without relying just on Display. My thought that having a lot of public surface being ok in this is just it's stat info on the trie structure that is probably very stable at this point. I'm also fine with limiting the exposed API to just Display though.

[Nashtare]

It's not really blocking, we can always restrict the API in the future. This isn't even on crates.io yet, is it?

[BGluth]

It's on crates.io, but it's been a while since we've pushed a new version. It's a pretty easy change for me to make, so for now I'll restrict the API a bit more,

[Nashtare]

Ah nevermind for crates.io, for some reason I thought this was eth-trie-tools 🤦🏼‍♂️