Add clientset for MPIJob, PytorchJob, MXJob, and XGBoostJob

[tenzen-y]

What this PR does / why we need it:
As discussed in here, I moved Kubernetes Custom Resource API codes to the pkg/apis/kubeflow.org/v1 directory to generate Go clientset for MPIJob, PytorchJob, MXJob, and XGBoostJob.

So, I made the following changes:

1. Move pkg/apis/[mpi|mxnet|pytorch|tensorflow|xgboost]/[v1|validation]/*.go to pkg/apis/kubeflow.org/v1/*.go.
2. Reduce duplication of codes for defaulting and validation tests.
3. Add a framework name prefix (ex. MPIJobDefaultPortName) to variable names that conflict between all frameworks.
4. Regenerate Go clientset, Python SDK, API documentation, and e2e test codes for all frameworks.
5. Update code to generate swagger file.
6. Update Readme.

Which issue(s) this PR fixes (optional, in Fixes #<issue number>, #<issue number>, ... format, will close the issue(s) when PR gets merged):
Fixes #1499, #1501, #1586, #1592

Checklist:

• Docs included if any changes are user facing

[coveralls]

Pull Request Test Coverage Report for Build 2482116121

• 345 of 2153 (16.02%) changed or added relevant lines in 36 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+4.5%) to 41.518%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/apis/kubeflow.org/v1/defaulting_utils.go	34	35	97.14%
pkg/controller.v1/pytorch/initcontainer.go	11	12	91.67%
pkg/controller.v1/tensorflow/util.go	12	13	92.31%
pkg/apis/kubeflow.org/v1/mxnet_defaults.go	30	33	90.91%
pkg/apis/kubeflow.org/v1/tensorflow_defaults.go	36	39	92.31%
pkg/apis/kubeflow.org/v1/xgboost_defaults.go	29	32	90.63%
pkg/controller.v1/pytorch/elastic.go	6	9	66.67%
pkg/apis/kubeflow.org/v1/mpi_defaults.go	0	4	0.0%
pkg/controller.v1/tensorflow/tfjob_controller.go	40	44	90.91%
pkg/controller.v1/register_controller.go	0	5	0.0%

Files with Coverage Reduction	New Missed Lines	%
pkg/controller.v1/mpi/mpijob_controller.go	2	77.8%

Totals
Change from base Build 2474657252:	4.5%
Covered Lines:	2298
Relevant Lines:	5535

---

💛 - Coveralls

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[tenzen-y]

@kubeflow/wg-training-leads Please take a look.

[tenzen-y]

/cc @zw0610

[tenzen-y]

I have grouped Go dependencies.

[tenzen-y]

I have updated links to API documentation in README.md.

[tenzen-y]

/cc @johnugeorge @gaocegege

[zw0610]

Thank you very much for your contribution! After the test passed, could you squash multiple commits into one?

[tenzen-y]

Thank you very much for your contribution! After the test passed, could you squash multiple commits into one?

Thanks for your comment! @zw0610
Sure, I will squash all commits into one.

[tenzen-y]

@zw0610 I have squashed all commits and passed all tests.

[johnugeorge]

/assign @zw0610
/assign @gaocegege

[johnugeorge]

@zw0610 @gaocegege Can you please review this so that we can get it in this release?

[zw0610]

LGTM
I went through the non-client parts. @gaocegege Could you also take a look at the clientset & python-client generation?

[gaocegege]

I think it is a breaking change for developers since the API packages are changed from gtihub.com/kubeflow/training-operator/pkg/apis/tensorflow/v1 to gtihub.com/kubeflow/training-operator/pkg/apis/kubeflow.org/v1

We should notice users in some degree

The PR itself LGTM

Thanks for your contribution! 🎉 👍

[tenzen-y]

@zw0610 @gaocegege Thanks for your review of this large PR!

I think it is a breaking change for developers since the API packages are changed from gtihub.com/kubeflow/training-operator/pkg/apis/tensorflow/v1 to gtihub.com/kubeflow/training-operator/pkg/apis/kubeflow.org/v1

We should notice users in some degree

I agree with you.

[zw0610]

this fix is long-overdue. Thank you again for this tremendous work.
/lgtm

[gaocegege]

@johnugeorge Could we merge it?

[johnugeorge]

Thanks everyone
/approve

[google-oss-prow]

[APPROVALNOTIFIER] This PR is APPROVED

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