Invalid key field when using getProof API

[JosephK95]

Description

When we execute getProof API, it returns an array of storage-entry objects as requested. According to the Ethereum API specification, the key field in the entry object should conform to ^0x([0-9a-f][0-9a-f]){0,32}$ regex pattern. However, it seems that Besu returns a non-conforming value.
(Specification link: https://github.com/ethereum/execution-apis)

Expected behavior:

{ 
  ...
  storageProof: [ { key: '0x2', value: '0x0', ... } ]
}

Actual behavior:

{ 
  ...
  storageProof: [ { key: '2', value: '0x0', ... } ]
}

Frequency:
Always

Versions (Add all that apply)

• Software version: besu/v22.4.4/linux-x86_64/openjdk-java-16
• OS Name & Version: Ubuntu 20.04.4 LTS

[non-fungible-nelson]

Hi there - is this bug present on Besu v22.7.0? @fab-10 @daniellehrner is this something we addressed in Hive testing?