Improved mapping of SICD polarizations to SIDD polarizations

[bombaci-vsc]

The SIDD types have a TxrcvPolarizationType.from_sicd_value() method which is responsible for mapping a SICD TxRcvPolarization value into separate SIDD Tx and Rcv values.

This mapping is not trivial. Each SIDD version supports a different list of valid values, and SICD has the concept of singular OTHER and UNKONWN values.

SICD v1.4	SIDD v1	SIDD v2	SIDD v3

For the cases where SICD provides both a transmit and receive polarization, I believe the mapping for each polarization should be:

SICD v1.4	SIDD v1	SIDD v2	SIDD v3
V	V	V	V
H	H	H	H
X	OTHER	OTHER	X
Y	OTHER	OTHER	Y
S	OTHER	OTHER	S
E	OTHER	OTHER	E
RHC	RHC	RHC	RHC
LHC	LHC	LHC	LHC
OTHER*	OTHER	OTHER	OTHER*

Then for the two sentinel values:

SICD v1.4	SIDD v1	SIDD v2	SIDD v3
OTHER	OTHER	OTHER	OTHER
UNKNOWN	OTHER	UNKNOWN	UNKNOWN

I've also fixed some bugs caused by the SIDD1 code reusing SIDD2, which would sometimes set the polarizations to "UNKNOWN" even though that isn't a valid value for SIDD v1.