feat: add unified api for CLI pull command

[zong-zhe]

1. Does this PR affect any open issues?(Y/N) and add issue references (e.g. "fix #123", "re #123".):

• N
• Y

re #289

2. What is the scope of this PR (e.g. component or file name):

3. Provide a description of the PR(e.g. more details, effects, motivations or doc link):

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Other

4. Are there any breaking changes?(Y/N) and describe the breaking changes(e.g. more details, motivations or doc link):

• N
• Y

5. Are there test cases for these changes?(Y/N) select and add more details, references or doc links:

• Unit test
• Integration test
• Benchmark (add benchmark stats below)
• Manual test (add detailed scripts or steps below)
• Other

[coveralls]

Pull Request Test Coverage Report for Build 9793195889

Details

• 106 of 724 (14.64%) changed or added relevant lines in 10 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-4.1%) to 40.261%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/cmd/cmd_push.go	0	1	0.0%
pkg/downloader/downloader.go	16	23	69.57%
pkg/package/modfile.go	9	18	50.0%
pkg/package/package.go	0	11	0.0%
pkg/client/client.go	34	52	65.38%
pkg/client/pull.go	46	64	71.88%
pkg/utils/utils.go	0	28	0.0%
pkg/downloader/toml.go	0	158	0.0%
pkg/downloader/source.go	0	368	0.0%

Files with Coverage Reduction	New Missed Lines	%
pkg/oci/oci.go	1	23.46%

Totals
Change from base Build 9791206524:	-4.1%
Covered Lines:	2592
Relevant Lines:	6438

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 9794141648

Details

• 107 of 735 (14.56%) changed or added relevant lines in 10 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-4.2%) to 40.208%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/cmd/cmd_push.go	0	1	0.0%
pkg/package/modfile.go	9	18	50.0%
pkg/package/package.go	0	11	0.0%
pkg/downloader/downloader.go	17	34	50.0%
pkg/client/client.go	34	52	65.38%
pkg/client/pull.go	46	64	71.88%
pkg/utils/utils.go	0	28	0.0%
pkg/downloader/toml.go	0	158	0.0%
pkg/downloader/source.go	0	368	0.0%

Files with Coverage Reduction	New Missed Lines	%
pkg/oci/oci.go	1	23.46%

Totals
Change from base Build 9791206524:	-4.2%
Covered Lines:	2593
Relevant Lines:	6449

---

💛 - Coveralls

[Peefy]

LGTM