Print canonical assembly for immediate loads/stores

Fix inconsistency in accessing PC/nextPC, which also clarifies which handlers return nextPC values as opposed to setting them.

Add base address register as extra argument to ext_data_check_addr hook

Push address calculation inside the data_check_addr hook and rename it to data_get_addr. This avoids a double register read in CHERI case.

Add base address register as extra argument to ext_data_check_addr hook to assist with implementing CHERI capability mode.

Remove unnecessary option in type of decode and decodeCompressed (never returned None because ILLEGAL ast value used for unknown instructions).

It turns out that the problem I was encountering with ARCH=32 was that I was setting it on the command line which overrides all assignments (including the ones that change it to RV32). Digging deeper down the Make rabbit hole it turns out that 'override' allows you to fix this.

Fix make code so that ARCH=32,64 actually works as expected (use := for immediate assignment to make variable).