v0.0.0-5041-gf4e0f594b

IWYU: Fix missing includes

Addressing the top missing includes:
  * xls/ir/value.h
  * xls/ir/bits.h
  * xls/ir/node.h
  * xls/ir/source_location.h
  * absl/types/span.h

Should fix at least around 1600 misc-include-cleaner warnings.

PiperOrigin-RevId: 629910777