feat(container): add waiters

[Codelax]

Closes #2936

[codecov-commenter]

Codecov Report

Merging #3098 (cb1087a) into master (3252886) will decrease coverage by 0.01%.
The diff coverage is 38.88%.

@@            Coverage Diff             @@
##           master    #3098      +/-   ##
==========================================
- Coverage   75.79%   75.78%   -0.01%     
==========================================
  Files         169      169              
  Lines       36631    36686      +55     
==========================================
+ Hits        27765    27804      +39     
- Misses       7903     7919      +16     
  Partials      963      963              

Impacted Files	Coverage Δ
...l/namespaces/container/v1beta1/custom_namespace.go	65.78% <26.66%> (+8.21%)	⬆️
...l/namespaces/container/v1beta1/custom_container.go	45.00% <38.88%> (+30.71%)	⬆️
internal/namespaces/container/v1beta1/custom.go	100.00% <100.00%> (ø)

... and 4 files with indirect coverage changes