fix(cuda): use vpmm v4

[gaxiom]

Updating to use openvm-org/stark-backend#179

Comparison bench: https://github.com/axiom-crypto/openvm-reth-benchmark/actions/runs/19803890244

[github-actions]

group	app.proof_time_ms	app.cycles	app.cells_used	leaf.proof_time_ms	leaf.cycles	leaf.cells_used
verify_fibair	(-19 [-7.9%]) 222	322,658	2,058,654	-	-	-
fibonacci	(+16 [+1.6%]) 1,010	1,500,209	2,100,402	-	-	-
regex	(+26 [+1.1%]) 2,365	4,137,502	17,695,216	-	-	-
ecrecover	(+2 [+0.3%]) 702	122,859	2,262,772	-	-	-
pairing	1,440	1,745,742	25,408,302	-	-	-

Commit: 2fefa42

Benchmark Workflow

[Copilot]

Pull request overview

This PR updates the stark-backend dependencies to v1.2.2-rc.0 to incorporate vpmm v4 improvements, as referenced in stark-backend PR #179. The workspace version is also bumped from 1.4.1 to 1.4.2-rc.0 to reflect this dependency update.

• Updates all 5 stark-backend git dependencies from tag v1.2.1 to v1.2.2-rc.0
• Bumps workspace package version from 1.4.1 to 1.4.2-rc.0
• Updates Cargo.lock with new commit hashes and version references

Reviewed changes

Copilot reviewed 1 out of 2 changed files in this pull request and generated no comments.

File	Description
Cargo.toml	Updates workspace version to 1.4.2-rc.0 and all stark-backend dependencies to v1.2.2-rc.0
Cargo.lock	Reflects the dependency updates with new versions and commit hashes for stark-backend packages and all workspace crates

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