ci: add a runner for vanilla LLVM 19

[cuviper]

Ubuntu 24.10 has llvm-19 packages that we can start testing with.
The Dockerfile is otherwise the same as the llvm-18 runner.

[rustbot]

r? @Mark-Simulacrum

rustbot has assigned @Mark-Simulacrum.
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[Mark-Simulacrum]

@bors r+ rollup=iffy

[bors]

📌 Commit 960ec52 has been approved by Mark-Simulacrum

It is now in the queue for this repository.

[bors]

⌛ Testing commit 960ec52 with merge 5e3ede2...

[bors]

☀️ Test successful - checks-actions
Approved by: Mark-Simulacrum
Pushing 5e3ede2 to master...

[rust-timer]

Finished benchmarking commit (5e3ede2): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

This benchmark run did not return any relevant results for this metric.

Cycles

Results (primary -5.4%, secondary 2.5%)

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.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	2.5%	[2.2%, 2.7%]	2
Improvements ✅ (primary)	-5.4%	[-5.4%, -5.4%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-5.4%	[-5.4%, -5.4%]	1

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 759.549s -> 760.71s (0.15%)
Artifact size: 341.18 MiB -> 341.13 MiB (-0.01%)