std: Back out backtrace pruning logic

[alexcrichton]

It was discovered #40264 that this backtrace pruning logic is a little too
aggressive, so while we figure how out to handle #40264 this commit backs out
the changes to prune frames. Note that other cosmetic changes, such as better
path printing and such remain.

[rust-highfive]

r? @BurntSushi

(rust_highfive has picked a reviewer for you, use r? to override)

[alexcrichton]

#40684 was the beta backport. This hasn't been applied to master yet but it looks like #40264 may go past the next cycle so I figured I'd send this to master as well.

[petrochenkov]

@bors r+

[bors]

📌 Commit e46a8bd has been approved by petrochenkov

[CryZe]

This might've unintentionally removed the message that shows that you can switch to a full backtrace with "RUST_BACKTRACE=full", because the logic for it checks whether frames got omitted:

rust/src/libstd/sys_common/backtrace.rs

Line 74 in 9f2abad

if skipped_before + skipped_after > 0 {

So this message never shows up.

[alexcrichton]

@CryZe that's somewhat intentional, the =full just adds in the addresses currently where the primary intention is to add in frames. No frames are ever omitted currently, so the utility of =full is somewhat reduced today.

[CryZe]

Ah okay, thanks for clarifying :)