Migrate to reconciler pattern for Build

[imjasonh]

Fixes #393

Proposed Changes

• Copy code out of pkg/controller/build/ and into pkg/reconciler/build/
• Make tests pass
• That's pretty much it.

This is a smaller, more mechanical change than #420 which attempted to roll in a refactor which would have let us drop builder.Interface. I'd still like to get rid of that abstraction and just always interact with a kubeClient (which might be fake in tests), but I'll get to that some time after 0.2.

/assign shashwathi
/assign mattmoor

Release Note

Migrate to reconciler pattern for Build 

[knative-prow-robot]

@imjasonh: 0 warnings.

In response to this:

Fixes #393

Proposed Changes

• Copy code out of pkg/controller/build/ and into pkg/reconciler/build/
• Make tests pass
• That's pretty much it.

This is a smaller, more mechanical change than #420 which attempted to roll in a refactor which would have let us drop builder.Interface. I'd still like to get rid of that abstraction and just always interact with a kubeClient (which might be fake in tests), but I'll get to that some time after 0.2.

/assign shashwathi
/assign mattmoor

Release Note

Migrate to reconciler pattern for Build 

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[shashwathi]

I definitely like the scope of this PR. Great work @imjasonh

[mattmoor]

thanks, @imjasonh! Glad to see Build picking this up!

/lgtm
/approve
/hold

Hold for one nit, if you want to address it now. If not, cancel the hold. I understand this is just the first step :)

[knative-prow-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ImJasonH, mattmoor

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [ImJasonH,mattmoor]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[knative-metrics-robot]

The following is the coverage report on pkg/.
Say /test pull-knative-build-go-coverage to re-run this coverage report

File	Old Coverage	New Coverage	Delta
pkg/reconciler/build/build.go	5.6%	76.4%	70.8
pkg/reconciler/build/template_common.go	Do not exist	100.0%
pkg/reconciler/build/validate_build.go	Do not exist	93.0%

[imjasonh]

/hold cancel

[mattmoor]

/lgtm