The use of "go install" is deprecated as a way of installing and running the
Mockery binary. Update the runner script to depend on an ambient version of the
tool and ensure that in CI it's installed.
This change aims to keep versions of mockery consistent across developer laptops.
This change adds mockery to the `tools.go` file so that its version can be managed consistently in the `go.mod` file.
Additionally, this change temporarily disables adding mockery's version number to generated files. There is an outstanding issue against the mockery project related to the version string behavior when running from `go get`. I have created a pull request to fix this issue in the mockery project.
see: https://github.com/vektra/mockery/issues/397