fix: add --set and --set-value-file flag support to delete command and unit tests

[bogdannazarenko]

Description
This PR adds support for the --set and --set-value-file flag to the skaffold delete command, allowing users to override templated manifest fields with key-value pairs during deletion operations.

Fixes #10053

Changes made:

1. Updated cmd/skaffold/app/cmd/flags.go line 764 to include "delete" in the DefinedOn list for the "set" and "set-value-file" flags
2. Created cmd/skaffold/app/cmd/delete_test.go with unit tests to verify that the delete command accepts --set, --set-value-file and --dry-run flags
3. Verified the built skaffold binary correctly accepts the --set and --set-value-file flag for the delete command

User facing changes
Users can now use the --set and --set-value-file flags with skaffold delete to override templated manifest fields:

Before: skaffold delete did not accept --set or --set-value-file flags
After: skaffold delete --set key=value --set set-value-file=file is now supported

This allows for more flexible deletion operations when working with templated manifests.

Testing

• Added unit test TestNewCmdDelete in delete_test.go that verifies both --set, --set-value-file and --dry-run flags are available
• All existing tests pass
• All linters pass

[gemini-code-assist]

Code Review

This pull request enables the --set flag for the skaffold delete command and introduces a unit test to verify the presence of the --set and --dry-run flags. Feedback suggests enhancing the test to verify flag binding and ensuring isolation by overriding package-level variables. Additionally, it is recommended to enable the --set-value-file flag for the delete command to maintain consistency with other commands that support manifest overrides.

[Darien-Lin]

Seems that the unit test require you to run: ./hack/generate-man.sh

[bogdannazarenko]

@Darien-Lin the failed integration tests are not related to these changes. Looks like they are pre-existing failures
https://github.com/GoogleContainerTools/skaffold/actions/runs/24786039920/job/72530549490?pr=10054#step:19:3587
https://github.com/GoogleContainerTools/skaffold/actions/runs/24786039920/job/72530549490?pr=10054#step:19:3529