Bump golangci-lint to v0.19.0

[corneliusweig]

Description

Bump golangci-lint to v0.19.0
This required to align receiver names as reported by stylecheck. Here, I opted for the one-letter short forms instead of the longer receiver names. Maybe for the configs this is not the right way?

User facing changes

n/a

Before

n/a

After

n/a

Next PRs.

n/a

Submitter Checklist

These are the criteria that every PR should meet, please check them off as you
review them:

• Includes unit tests
• Mentions any output changes.
• Adds documentation as needed: user docs, YAML reference, CLI reference.
• Adds integration tests if needed.

See the contribution guide for more details.

Double check this list of stuff that's easy to miss:

• If you are adding a example to the examples dir, please copy them to integration/examples
• Every new example added in integration/examples dir, should be tested in integration test

Reviewer Notes

• The code flow looks good.
• Unit test added.
• User facing changes look good.

[codecov]

Codecov Report

Merging #2927 into master will not change coverage.
The diff coverage is 84.05%.

Impacted Files	Coverage Δ
pkg/skaffold/sync/sync.go	75% <0%> (ø)	⬆️
pkg/skaffold/schema/v1beta10/upgrade.go	100% <100%> (ø)	⬆️
pkg/skaffold/schema/v1beta11/upgrade.go	100% <100%> (ø)	⬆️
pkg/skaffold/schema/v1alpha3/upgrade.go	100% <100%> (ø)	⬆️
pkg/skaffold/schema/v1beta7/upgrade.go	100% <100%> (ø)	⬆️
pkg/skaffold/schema/v1alpha5/upgrade.go	100% <100%> (ø)	⬆️
pkg/skaffold/schema/v1beta1/upgrade.go	100% <100%> (ø)	⬆️
pkg/skaffold/schema/v1alpha4/upgrade.go	100% <100%> (ø)	⬆️
pkg/skaffold/schema/v1beta6/upgrade.go	100% <100%> (ø)	⬆️
pkg/skaffold/schema/v1beta12/upgrade.go	100% <100%> (ø)	⬆️
... and 9 more

[tejal29]

LGTM