Renaming in codebase to match new name "step" on UI

[NickOpenFn]

Rename Runs to Steps
Rename AttemptRuns to AttemptSteps

Do not rename Attempts to Runs as this is non-blocking and can only happen after this issue is closed. We'll track that second issue elsewhere, and it's lower priority than this one.

Next issue: #1657

[taylordowns2000]

needs some discussion:

running stuff

v0.10: work order > attempt > attempt_run <> run
v2:    work order > run     > run_step    <> step

building stuff

v0.10: project > workflow > job
v2: project > workflow > job (but we also refer to it as a 'step' in the UI)

note that “step” as used in the UI is super contextual: if you’re looking at a workflow, step means the little boxes/jobs.
if you’re looking at a run, step means the instances of execution of those little boxes/jobs during this run.

[taylordowns2000]

given how expensive engineering work will get while this isn't finished, i'd vote we put this at the top of the backlog as soon as @stuartc is back and we're 100% aligned on the names. as expected, we've already had a number of costly back-and-forth conversations and bugs related this one.

sheet with naming proposal: https://docs.google.com/spreadsheets/d/1CtFq5fwZ_UtZ7r7Kam96Ja_3ixVNpT0dal3_EClPyiM/edit#gid=0

[taylordowns2000]

Hey team! Please add your planning poker estimate with Zenhub @elias-ba @jyeshe @midigofrank @stuartc

[stuartc]

My advice here is to start with Run -> Step, break it via renaming/changing the module name.

Change the relationship names (while perhaps overriding the foreign keys value), and delaying the migrations as much as possible.