Copy over most of the workflows from pulumi-ci-mgmt (#29)

* Copy over most of the workflows from pulumi-ci-mgmt

* Remove publish workflow

* Copy over generated PR workflow

* Codegen target

* Set repo for schema-tools

* Remove other extraneous workflows

* Set github token

* Copy over regenerated workflows

* Regen workflows yet again

* Remove make dep

* Use pulumi bin if it exists

* Build test image