Push ${xd.stream.name} into POJO defaults

See XD-1283.
We've been waiting for 1283 to change constructs like

attr="${name:${xd.stream.name}}"

to just

attr="${name}"

Turns out we can simply push down the ${xd.stream.name} bit in the default value (most likely initialization of a field in a POJO metadata class) and it will work just fine.

We can also consider:

• providing a fake value for those placeholders to use when doing "module info" (ie user will see "<name of the stream>" instead of "${xd.stream.name}"