[kernel] Remove #if WITH_LIB_* conditionals

There's only one configuration of the kernel per architecture, so these
are always defined anyway. The global predefines based on what modules
are in the dependency graph is not a feature future build systems will
support.

Test: CQ & manual verification that kernel text size didn't change
Change-Id: Ib4c9b6c309c9ae4fc410701eef8fbdfad4d90641

[kernel] Remove some __USED workarounds for LTO bugs

The LTO compiler has been fixed so these attributes are no longer
needed to prevent symbols being dropped.

Test: CQ & local LTO build (arm64)
Change-Id: Ic36a2770e7637a5b625514e529fe846f6898ab8c

[kernel][cpp] convert a few more libs (debug, version) to cpp

Also ran the formatter at the same time, since these are such simple
files.

Change-Id: Ib9f80e5c1ff9f98517beea93f6cd42aa75e20576