Misc. fixes to make cava compile

• Add max / min intrinsics
• DC substitution leaves phantom invalid DCs that are never referenced; skip these DCs in bottom up iteration over all DCs
• Separate analysis for device placement, can be used in backends to know where other functions are placed
• Support AsyncRust functions calling other AsyncRust functions, as well as other LLVM functions
• Fix the names of a bunch of tests, call still works when not inlining in AsyncRust functions
• Comment out forkify and forkguardelim since they are known broken, and were preventing cava from working

requested review from @aaronjc4

assigned to @rarbore2

mentioned in commit 19c7dde3

merged