Update backtrace

[saethlin]

Most notably, this pulls in rust-lang/backtrace-rs@ebc9a85, which is both a bugfix and a significant performance improvement for Miri, since fixing the bug makes RUST_BACKTRACE=1 backtraces much smaller: rust-lang/miri#2273, rust-lang/miri-test-libstd#8

This also pulls in other commits which turn the backtrace-rs CI green. That's nice.

[rust-highfive]

r? @Mark-Simulacrum

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[rust-highfive]

⚠️ Warning ⚠️

• These commits modify submodules.

[Mark-Simulacrum]

@bors r+ rollup=iffy

[bors]

📌 Commit a7b4f18 has been approved by Mark-Simulacrum

It is now in the queue for this repository.

[bors]

⌛ Testing commit a7b4f18 with merge dec6894...

[bors]

☀️ Test successful - checks-actions
Approved by: Mark-Simulacrum
Pushing dec6894 to master...

[rust-timer]

Finished benchmarking commit (dec6894): comparison URL.

Overall result: ✅ improvements - no action needed

@rustbot label: -perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean1	range	count2
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.1%	[-1.1%, -1.1%]	1
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean1	range	count2
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	3.9%	[2.6%, 5.9%]	5
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Cycles

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean1	range	count2
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-2.9%	[-2.9%, -2.9%]	1
Improvements ✅ (secondary)	-4.7%	[-4.7%, -4.7%]	1
All ❌✅ (primary)	-2.9%	[-2.9%, -2.9%]	1

Footnotes

1. the arithmetic mean of the percent change ↩ ↩² ↩³

2. number of relevant changes ↩ ↩² ↩³