Warp route deployer should derive scale factor from decimal config

[yorhodes]

Problem

#5233 introduces scaling to fungible warp routes.

There is an optional scale field on the TokenMetadataSchema for configuring this value (default is 1).

When a warp route is configured with non-uniform decimals, the scale value should be validated and derived to ensure that the warp route is correctly scaled.

Solution

Given some config

chainA:
    ...
    decimals: 18
chainB:
    ...
    decimals: 6

The scale value should be derived as follows:

const messageDecimals = Math.max(chainA.decimals, chainB.decimals); // 18
const scaleA = 10 ** (messageDecimals - chainA.decimals); // 10^0 = 1
const scaleB = 10 ** (messageDecimals - chainB.decimals); // 10^12