Add unwrap method to MoveItems
mark win32 binaries as large address aware

By default, 32-bit Windows executables are restricted to 2GiB of address
space even when running on 64-bit Windows when 4GiB is available.

Closes #17043
auto merge of #17053 : thestinger/rust/large_address_aware, r=sfackler,cmr

By default, 32-bit Windows executables are restricted to 2GiB of address
space even when running on 64-bit Windows when 4GiB is available.

Closes #17043
auto merge of #16903 : mahkoh/rust/move_items_unwrap, r=aturon

Closes #16879
auto merge of #12809 : eddyb/rust/ty-arena, r=cmr

This was inspired by seeing a LLVM flatline of **~600MB** when running rustc with jemalloc (each type's `t_box_` is allocated on the heap, creating a lot of fragmentation, which jemalloc can deal with, unlike glibc).
Remove largely unused context from Visitor.
Track the visited AST's lifetime throughout Visitor.