[wheel] Add an option for --snopt-path

[jwnimmer-tri]

This puts the git credentials step up-front in the build (prior to Docker or running as root) the same as any normal local build would need. This makes automating wheel builds easier, e.g., in GitHub Actions. The wheel's inner CMake build step always uses a snopt.tar.gz archive provided by our wrapper scripts.

Closes #21574.

I tested this PR using GitHub actions here: https://github.com/jwnimmer-tri/drake_github_workflow_prototype/commits/main/

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This change is 

[jwnimmer-tri]

@drake-jenkins-bot linux-jammy-unprovisioned-gcc-wheel-experimental-release please @drake-jenkins-bot mac-arm-ventura-unprovisioned-clang-wheel-experimental-release please

[jwnimmer-tri]

@drake-jenkins-bot linux-jammy-unprovisioned-gcc-wheel-experimental-release please @drake-jenkins-bot mac-arm-ventura-unprovisioned-clang-wheel-experimental-release please

[jwnimmer-tri]

@drake-jenkins-bot mac-arm-ventura-unprovisioned-clang-wheel-experimental-release please

[jwnimmer-tri]

@drake-jenkins-bot mac-arm-ventura-unprovisioned-clang-wheel-experimental-release please

[jwnimmer-tri]

@drake-jenkins-bot linux-jammy-unprovisioned-gcc-wheel-experimental-release please

[jwnimmer-tri]

+@rpoyner-tri for feature review, please. No particular hurry, the only goal is to land this before the next release.

(I'll squash the commits when I next push, or else when we merge.)

[jwnimmer-tri]

+@xuchenhan-tri for platform review, please (as you have at least some build-system experience).