Courts hierarchy merge - avoid collision between xDai and Ethereum court IDs on Arbitrum

[jaybuidl]

Problem

Requires a translation mechanism on xDai to map the court IDs to Arbitrum court IDs without collision with the mainnet ones.

There should be only 1 General court.

Solution

There is no way to predict the v2 courtId based on v1 courtId so we must implement a mapping maintained via governance.

The conversion from v1 to v2 courtIds must take place in the xKlerosLiquidV2 adapter.
The conversion cannot take place in the ForeignGateway because the FG assumes incoming messages are v2 ones.

CourtId conversion table:

Consolidated hierarchy looks as follow: