More dynamic casting tests (#34732)
More dynamic casting tests (#34732)

Add regression tests for a number of casting cases that were fixed by recent work:

* SR-13812 (aka rdar://70999129)

Verify that the new casting logic correctly handles
a generic `is` test for a struct conforming to a protocol.

* SR-8964 (aka rdar://45217461)

Test casts from Any! holding Error types

* SR-1999 (aka rdar://48769924)

* SR-6279 (aka rdar://35321438

* rdar://59844232

* SR-12025

Note that SR-12025 is not actually fixed yet; this test is marked "expected failure" until it is.

glessard/swift,apple/swift,apple/swift,roambotics/swift,ahoppen/swift,hooman/swift,gregomni/swift,hooman/swift,ahoppen/swift,parkera/swift,ahoppen/swift,glessard/swift,benlangmuir/swift,tkremenek/swift,parkera/swift,jmgc/swift,JGiola/swift,hooman/swift,roambotics/swift,rudkx/swift,gregomni/swift,apple/swift,apple/swift,rudkx/swift,roambotics/swift,benlangmuir/swift,jmgc/swift,xwu/swift,glessard/swift,benlangmuir/swift,parkera/swift,tkremenek/swift,xwu/swift,roambotics/swift,jmgc/swift,parkera/swift,JGiola/swift,xwu/swift,hooman/swift,xwu/swift,hooman/swift,JGiola/swift,roambotics/swift,tkremenek/swift,ahoppen/swift,atrick/swift,ahoppen/swift,rudkx/swift,hooman/swift,roambotics/swift,gregomni/swift,ahoppen/swift,JGiola/swift,JGiola/swift,benlangmuir/swift,xwu/swift,rudkx/swift,benlangmuir/swift,tkremenek/swift,jmgc/swift,gregomni/swift,glessard/swift,tkremenek/swift,gregomni/swift,atrick/swift,parkera/swift,atrick/swift,gregomni/swift,benlangmuir/swift,parkera/swift,atrick/swift,parkera/swift,xwu/swift,parkera/swift,glessard/swift,apple/swift,jmgc/swift,atrick/swift,tkremenek/swift,rudkx/swift,atrick/swift,apple/swift,glessard/swift,tkremenek/swift,rudkx/swift,JGiola/swift,jmgc/swift,jmgc/swift,xwu/swift,hooman/swift