Account Unification CE and Precompile

[ashutoshvarma]

Even with AU enabled for user, wasm smart contract has no way to get his/her mapped evm address, that makes it impossible to approve/transfer assets on his behalf using XVM since we don't know what his/her evm address will be in order to construct the XVM call to ERC20 evm contract

Solution: Add a getter method in XVM a new CE & Precompile for AU to fetch the mapped address from AU respectively.

Originally posted by @ashutoshvarma in #1033 (comment)

Tasks,

• Implement CE with getters to read mappings - feat(AU): charge storage fee and add initial CE #1058
• Implement Precompile with getters to read mappings - Feat/au precompile #1080

[andabak]

@ashutoshvarma - is this PR missing lables for target runtimes?

[ashutoshvarma]

@andabak This is a issue and the PRs addressing this issue has the target runtime labels

• Feat/au precompile #1080
• feat(AU): charge storage fee and add initial CE #1058