New input for installing a specific emulator version

[ofalvai]

Checklist

• I've read and followed the Contribution Guidelines
• step.yml and README.md is updated with the changes (if needed)

Version

Requires a MINOR version update

Context

The emulator SDK package is not versioned and there is no way to sdkmanager --install a specific version, it always installs the latest version.

We regularly update the emulator package to the latest version because of the above. New updates frequently introduce bugs, performance regressions, but also fixes to those regressions, so there is no "good" emulator version, it's better to provide a preinstalled default and let users override it at runtime.

Changes

• Add a mechanism to download and install a specific version at runtime. This is largely based on the hacky instructions from Google
• Introduce a new input: emulator_build_number. This could cause a conflict with the existing emulator_channel input, so there is new extra validation for this edge case.
• Update go-utils and go-steputils (needed because of the newly imported subpackages)
• Input category cleanups

Investigation details

Decisions