[v0.4.19] Dependency bumps, fix environment variables used by mage

[HarrisonWAffel]

• Bumps several dependencies to the latest versions
• Fixes the PR workflow to only run on PRs
• Fixes the mage file to ensure the arch specified in NewGo is actually used. Currently, the host architecture is always being used as ARCH was being set instead of GOARCH

Notes:

• github.com/Microsoft/hcsshim cannot be bumped at this time as the indirect github.com/prometheus dependencies rely on a type within the k8s.io/component-base dependency which was made private in 1.29. This is fixed in version v0.31.1. When we bump all k8s dependencies to v0.31.1 we can also bump github.com/Microsoft/hcsshim
• A few other dependencies in the replace block have more recent versions, but have not been bumped so as to align with the latest versions used by the system-agent

[HarrisonWAffel]

Merging with a single review as these are simple go.mod bumps and trivial updates to the mage tools