Dump flags lack test coverage

Many ddump-* flags have no test coverage.

Examples (not an exhaustive list):

• ddump-cmm-raw
• ddump-cmm-cfg
• ddump-cmm-cbe
• ddump-cmm-switch
• ddump-cmm-proc
• ddump-cmm-sp
• ddump-cmm-sink
• ddump-cmm-caf
• ddump-cmm-procmap
• ddump-cmm-split
• ddump-cmm-info
• ddump-cmm-opt
• ddump-cfg-weights
• ddump-asm-native
• ddump-asm-liveness
• ddump-asm-regalloc
• ddump-asm-conflicts
• ddump-asm-regalloc-stages
• ddump-asm-stats
• ddump-c-backend
• ddump-faststrings
• ddump-foreign
• ddump-call-arity
• ddump-view-pattern-commoning
• ddump-stg-unarised
• ddump-stg-tags
• falignment-sanitisation
• fllvm-fill-undef-with-garbage
• fproc-alignment

There are a few which have tests (ddump-cmm, ddump-core-stats, ddump-asm etc.), but I claim every flag that we list in the manual should have some coverage.

Motivation: I'm attempting to decouple code output from pretty-printing as described in #21853 (closed). This involves changing the way we pretty-print CLabels. At the moment, dumping uses a different style than code output: PprDump vs PprCode, and always prints labels using CStyle, which seems haphazard. I will be assuming that for those functions, the style doesn't matter in the end, but it feels awkward.