fix: update deps, go version, and tests

[jghiloni]

This PR addresses the following issues:

• Updates the go toolchain from 1.21 (unsupported) to 1.25.10 (the current oldest supported version)
• Updates BurntSushi/toml
• Updates from the no-longer-maintained gopkg.in/yaml.* packages to go.yaml.in/yaml/*
• Updates the GH workflow to use the latest versions of actions
• Updates the GH workflow to use go version alias oldstable instead of 1.18
• Updates the tests to reflect that the new version of BurntSushi/toml outputs inf instead of +inf

[sclevine]

@jghiloni failing CD build

[jghiloni]

Helps when you use the right name