* All: Drop 'basic-blocks' feature
This makes it so that 'basic-blocks' cannot be disabled and we can
start assuming it everywhere.
* Tests: Replace non-bb filetests with bb version
* Tests: Adapt solver-fixedconflict filetests to use basic blocks
When using basic block instructions cannot be added in-between jump instructions which are ending basic blocks. These changes create extra basic blocks such that extra space is available for the spilling and moving registers where they are expected.
-Add resumable_trap, safepoint, isnull, and null instructions
-Add Stackmap struct and StackmapSink trait
Co-authored-by: Mir Ahmed <mirahmed753@gmail.com>
Co-authored-by: Dan Gohman <sunfish@mozilla.com>
