Add ./check.sh script

Add ./check.sh script

Running `mage check` takes too long time for user (and agent) iterations. That will eventualy run on CI.

This is a faster version that:

* Checks gofmt.
* Runs go vet.
* Runs staticcheck.
* Runs unit tests without the race flag.

It assumes that Go is installed, but will check if staticcheck is available and install it if not with go install.

It takes an optional argument to specify packages to check, otherwise it checks all packages.

This commit also enable local runs of the image golden tests.