weave-runtime: should we go with 12 decimal places or 15 or 18?

[amarts]

currently weave has below configuration:

    pub const WAY: Balance = 1_000_000_000_000;
    pub const UNITS: Balance = WAY;

ie, is 12 decimal point precision. But our weights for few runtimes are coming to 1+ UNITS already, which may be be an accounting challenge. Would prefer this to be at least 15 decimal point (ie, 0.001-0.01 UNITS for transaction) or 18, which means it is 1 uUNITS.

thoughts welcome.

@smohan-dw