Ensure ErasedData only implements appropriate auto traits

[Zoxc]

This uses an external type to prevent auto traits to be inferred on ErasedData. That inference is incorrect since it may not store the type it declares.

This also implements DynSend and DynSync on ErasedData which are checked by bounds on erase_val.

Some diagnostics bounds were missing DynSync, which is also added here.

[rustbot]

r? @nnethercote

rustbot has assigned @nnethercote.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

Why was this reviewer chosen?

The reviewer was selected based on:

• Owners of files modified in this PR: compiler
• compiler expanded to 69 candidates
• Random selection from 12 candidates

[Zoxc]

cc @petrochenkov @Zalathar

[Zoxc]

@bors try @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

@rustbot label: +S-waiting-on-perf

[rust-bors]

⌛ Trying commit b0ccfe9 with merge 87b89de…

To cancel the try build, run the command @bors try cancel.

Workflow: https://github.com/rust-lang/rust/actions/runs/23415439054