Improve error handling in build v2 repo

[routerhan]

Idea:

Mainly for the buildrun controller, we have different places where we return 2 errors during reconciliation. Where one of those errors can be nil, which is very misleading when reading the operator logs.

Example of the above is https:/redhat-developer/build/blob/master/pkg/controller/buildrun/buildrun_controller.go#L116

Expected result:

• Only return multiple errors if each error is not nil.

[routerhan]

@qu1queee for your reference.

[Avni-Sharma]

Also, proper logging required on errors, for eg, as mentioned here https:/redhat-developer/build/blob/56dc0293ae24813e70efc25c352b67117590b540/pkg/controller/buildrun/buildrun_controller.go#L183

[qu1queee]

Adding this to #174 for a short discussion(shouldnt take more than 1 min)

[routerhan]

Pls refer to this PR for more discussion : #220

[zhangtbj]

PR is merged. Thanks @routerhan