refactor: replace 4d63.com/tz with time/tzdata

[pmalek]

Description

Looking at https://github.com/leighmcculloch/go-tz ( 4d63.com/tz import path

skaffold/go.mod

Line 32 in aa6f5a3

4d63.com/tz v1.2.0

) it seems that the repo is unmaintained:

Deprecated: Use time/tzdata available in Go 1.15. time/tzdata does not work exactly the same as it defaults to local tzdata when available where as this package always uses embedded data. This package will be maintained until Go 1.16 is released.

This PR replaces usage of that package with time/tzdata by include a build tag timetzdata as suggested at https://pkg.go.dev/time/tzdata. An alternative is to import time/tzdata as suggested:

This package should normally be imported by a program's main package, not by a library. Libraries normally shouldn't decide whether to include the timezone database in a program.

Open questions

Tests at https://github.com/GoogleContainerTools/skaffold/blob/main/pkg/skaffold/tag/date_time_test.go seem to pass (at least locally). Do we want to include more for this change?

[aaron-prindle]

@pmalek thanks for the PR here, LGTM! The tests you updated should be enough here.