CRD Strategy: implement concurrencyPolicy

[eytan-avisror]

Fixes #1

• This implements concurrencyPolicy to lock currently running workflows/CR.
• Added some doc/example fixes

Testing done

• Unit tests passing
• Full bdd test testing
• Manually ran rollingupgrades with InstanceGroup AMI changes and only a single CR was processed at a time.

[codecov-io]

Codecov Report

Merging #6 into master will decrease coverage by 3.13%.
The diff coverage is 53.39%.

@@            Coverage Diff             @@
##           master       #6      +/-   ##
==========================================
- Coverage   69.37%   66.23%   -3.14%     
==========================================
  Files           5        5              
  Lines         542      616      +74     
==========================================
+ Hits          376      408      +32     
- Misses        122      154      +32     
- Partials       44       54      +10

Impacted Files	Coverage Δ
...ontrollers/provisioners/ekscloudformation/types.go	63.07% <50%> (-1.84%)	⬇️
...rollers/provisioners/ekscloudformation/strategy.go	50.81% <52%> (-5.31%)	⬇️
...trollers/provisioners/ekscloudformation/helpers.go	60% <60%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 370d88f...4c21651. Read the comment docs.

[vgunapati]

LGTM 🚀

[kevdowney]

LGTM. Some minor comments.