Tooling refactor

[paulfantom]

• Use jsonnet-bundler 0.4.0
• Add a Makefile for simplicity
• Use go.mod to lock tools to specific versions
• Use temporary directory to store tooling binaries
• Speed up cloning mixin by remove --filter
• switch to github actions and remove drone ci pipeline (switch is done to simplify credentials handling)
• add daily CI cron job to regenerate mixins

[paulfantom]

@brancz @metalmatze wdyt?

[brancz]

neat, sgtm