Update Go to 1.17

[ivan-valkov]

Go 1.17 was released recently. It comes with a number of changes but something that might be of particular interest to us is the "free" ~5% performance improvement we can get. It comes from the new way of passing function arguments and results implemented in the go compiler.

I believe the easiest way to do this will be to bump the go version in the core builder and build a new version.
We can also consider bumping the go version specified in our go.mod files in the executor and operator.

[ukclivecox]

we have now moved to go 1.16 so this should be easier to look into.