When a heroku_build fails, query & output the build error

[mars]

When a heroku_build fails, the existing error message contains a short-lived URL to download the build log. This is a frustrating experience, to have to go fetch the build log separately each time.

The changeset automatically fetches the URL and sets the complete build log into the error message, so that it appears inline with all other Terraform output.

Example new heroku_build error output, from the the acceptance test case:

        Error: Build failed (app: 58203794-bbca-499d-af42-a6c1870d1909), complete build log follows:
        
        -----> Building on the Heroku-20 stack
        -----> Determining which buildpack to use for this app
        -----> Ruby app detected
        -----> Installing bundler 1.17.3
        -----> Removing BUNDLED WITH version in the Gemfile.lock
        -----> Compiling Ruby
        
         !
         !     There was an error parsing your Gemfile, we cannot continue
         !     
         !     #  from /tmp/build_25aef0c6/Gemfile:3
         !     #  -------------------------------------------
         !     #
         !     >  <<<<<<< Intentional syntax error to break the build
         !     #
         !     #  -------------------------------------------
         !
         !     Push rejected, failed to compile Ruby app.
        
         !     Push failed
        
        (End of build log)

Also includes a Terraform plugin SDK upgrade, because it was throwing error: unsupported state format version: expected ["0.1" "0.2"], got "1.0".

[mars]

I'll be replacing the Heroku service account & team GitHub Action secrets this week, so that CI can run successfully again.