[FEATURE] - Add string constant support for XTS macro

[RonniePitts]

In the XTS macro we need to specify the SATELLITE name as an additional column which typically exists in the staging macro as the below example shows :

These additional devised columns can be painful when multiple satellite are sourced from the staging model.

My feature is to support a string constant as we do in the staging macro which would allows us to reference a macro to return the node name.

For example:
src_satellite:
SAT_CUSTOMER_DETAILS:
sat_name:
SATELLITE_NAME: '!{{get_satobject(this}}}'
hashdiff:
HASHDIFF: CUSTOMER_HASHDIFF

get_satobject receives the SAT_CUSTOMER_DETAILS node and returns the node name of which is SAT_CUSTOMER_DETAILS given this is typically what the string constant name is in the staging model derived fields anyhow.

AB#5362