Tracking issue for cleaning up core's and std's panic machinery

[m-ou-se]

We can probably clean a bunch of things up in library/core/src/panic.rs, library/core/src/panicking.rs, library/core/src/panic/panic_info.rs, library/std/src/panic.rs and library/std/src/panicking.rs.

Here's an attempt of a sketch of the situation today:

(Edit: last diagram update: 2023-09-21)

(Note that a bunch of the complexity is the implementations of some of these functions, which is not visible in this diagram.)

• Make PanicInfo::message available in all situations Make PanicInfo::message infallible #115561
• Clear up confusion about 'message' (available in #[panic_handler]) and 'payload' (available in panic hook)
  • By splitting PanicInfo into two types? Split core's PanicInfo and std's PanicInfo #115974
• Add payload_as_str method: Tracking Issue for PanicHookInfo::payload_as_str() #125175
• Call panic_display directly in const_panic_fmt. #116007
• Use clearer naming internally
  • Rename BoxMeUp to PanicPayload. #116008
  • Rename r#try to catch_unwind: rename 'try' intrinsic to 'catch_unwind' #121598
  • Rename rust_panic_without_hook to resume_unwind
  • Remove unnecessary rust_ prefixes
  • Find a better name for begin_panic
  • Rename begin_panic_handler to just panic_handler
• Simplify more things
• Document more things
• ...