Add scaling support for UART instances to UART2CC26X2

CC13X4, CC26X4, and CC26X3 add two new UART instances vs X2 devices. This means that IO muxing and the Power manager ID selection need updating.

Currently, those are generated at runtime. That worked well enough when there were only two (or one on X1 devices). But at four instances, we should try to solve this through improved data structures rather than through just code.

We should add the Power manager ID, the tx mux settings, and the rx settings to the device-specific HWAttrs and then populate them through SysConfig.

This change results in a compatibility break to UART2CC26X2_HWAttrs. In order to populate the new fields, you just need to rerun your SysConfig generation.