[ci] Use small circleci resource class for all jobs

[Kyle-Verhoog]

As per title. This should help minimize costs on circleci and shouldn't come at too much a performance hit since the tests are not run in parallel.

Unfortunately it doesn't look like we can set a default resource class for all jobs, so we have to specify one for each job 😕.

[brettlangdon]

We should be able to do something like this:

default_job: &default_job
    docker:
        - *test_runner
    resource_class: *resource_class


jobs:
    flake8:
        <<: *default_job
        steps:
          - ...

YAML has some issues with block inheritance though, since if you wanted to add to docker: your changes overwrite those from default_job instead of merging.

default_job: &default_job
    docker:
        - *test_runner
    resource_class: *resource_class

jobs:
    flake8:
      <<: *default_job
      docker:
          - *test_runner
          - <custom thing>
      steps:
          - 

This isn't a required change to make in this PR, just an observation on the weirdness of YAML.

[brettlangdon]

great, thanks! and the tests pass too!