fix: lib/trie: fix trie.NextKey

[noot]

Changes

• re-implement trie.NextKey to work properly (and handle keys not in the trie)
• utilize trie.NextKey in runtime storage
• tested w/ kusama blocks that previous broke and works, also greatly increases the speed

Tests

go test ./lib/trie
go test ./lib/runtime/wasmer

Checklist

• I have read CODE_OF_CONDUCT and CONTRIBUTING
• I have provided as much information as possible and necessary
• I have reviewed my own pull request before requesting a review
• All integration tests and required coverage checks are passing

Issues

• closes fix and enable trie.NextKey #1439

[arijitAD]

I have added a test for the next trie key which seems to fail.

Test Commit

Also, the test seems to fail if I add an empty string to the test case. Not sure if it's a valid scenario.

[noot]

@arijitAD I made an update so that there are no duplicate keys in the test list and looks like it's good now!

[arijitAD]

Approved. Nice work 👌