Store a list of argument effects in a function, which specify if and how arguments escape.
Such effects can be specified in the Swift source code (for details see docs/ReferenceGuides/UnderscoredAttributes.md) or derived in an optimization pass.
For details see the documentation in SwiftCompilerSources/Sources/SIL/Effects.swift.
Improve block/instruction lists and similar collections
* pretty print collections in the form “[a, b, c]”
* also do this for lazy sequences
* define a custom Mirror
* in a collection, only print the name of blocks, functions and globals (instead of the full object)
* replace `BasicBlock.reverseInstructions` with `BasicBlock.instructions.reversed()` - in an efficient way
