feat: add mod push command impl

[adohe]

What type of PR is this?

/kind feature

What this PR does / why we need it:

add mod push command impl

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

will add test cases in the future

Does this PR introduce a user-facing change?

Additional documentation e.g., design docs, usage docs, etc.:

[coveralls]

Pull Request Test Coverage Report for Build 8326331634

Details

• 32 of 375 (8.53%) changed or added relevant lines in 11 files are covered.
• 5 unchanged lines in 3 files lost coverage.
• Overall coverage decreased (-1.6%) to 61.008%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/oci/reference.go	0	1	0.0%
pkg/modules/proto/module_grpc.pb.go	0	2	0.0%
pkg/oci/client/tag.go	0	6	0.0%
pkg/oci/metadata/metadata.go	0	9	0.0%
pkg/oci/client/push.go	0	12	0.0%
pkg/oci/client/client.go	0	19	0.0%
pkg/util/gitutil/info.go	0	22	0.0%
pkg/util/executable/executable.go	8	39	20.51%
pkg/oci/sign_artifact.go	0	55	0.0%
pkg/cmd/mod/mod_push.go	23	209	11.0%

Files with Coverage Reduction	New Missed Lines	%
pkg/engine/operation/watch.go	1	85.93%
pkg/cmd/mod/mod_push.go	1	13.43%
pkg/engine/operation/parser/parser.go	3	79.27%

Totals
Change from base Build 8325991978:	-1.6%
Covered Lines:	7410
Relevant Lines:	12146

---

💛 - Coveralls

[SparkYuan]

lgtm