Added BuildSource migration logic

[psrvere]

This PR includes migration of BuildSoure Type in BuildConfig to Shipwright equivalent specs. Following is the filed level status:

Field Name	Status	Notes
BuildSourceType		Ignored. It is not used by BuildConfig Code Logic
BinaryBuildSource
Files	✅
Archive	❌	Not supported in Shipwright
Dockerfile	❌	(Inline Dockerfile) Build-1495
GitBuildSource	✅
Images
Single Image	✅
Multiple Images	❌
As (alias) field	❌
Paths field	❌
From field	✅
PullSecret field	✅
ContextDir	✅
SourceSecret	✅
Secrets	❌	RFE - Under Discussion
ConfigMaps	❌	RFE - Under Discussion

This PR also unifies logic for "from" field processing for docker and source strategy and corrects the implementation.

Here are the detailed notes

[jmontleon]

ACK / LGTM

[jmontleon]

A couple of the test failures can be fixed pretty easily, I think:

diff --git a/convert/buildconfigs_test.go b/convert/buildconfigs_test.go
index 24475bc..e7818f3 100644
--- a/convert/buildconfigs_test.go
+++ b/convert/buildconfigs_test.go
@@ -236,7 +236,9 @@ func TestProcessSource(t *testing.T) {
 
        for _, tt := range tests {
                t.Run(tt.name, func(t *testing.T) {
-                       co := &ConvertOptions{}
+                       co := &ConvertOptions{
+                               logger: logrus.New(),
+                       }
                        build := &shipwrightv1beta1.Build{}
 
                        co.processSource(tt.buildConfig, build)
@@ -808,7 +810,7 @@ func TestProcessSourceStrategyFromField(t *testing.T) {
 
                err := co.processStrategyFromField(bc, build)
                assert.Error(t, err)
-               assert.Contains(t, err.Error(), "source strategy From kind Unknown is unknown for BuildConfig test-bc")
+               assert.Contains(t, err.Error(), "strategy 'From' kind Unknown is unknown type Source for BuildConfig test-bc")
                assert.Equal(t, 0, len(build.Spec.ParamValues))
        })

There is a third if I am not mistaken because a ParamValue is no longer being set and either should be adjusted or removed.

[psrvere]

Thanks @jmontleon for the review. I have fixed the tests and these are passing now.