feat: add cache for credential to reduce the probability that kpm would be considered a threat

[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 https://github.com/orgs/kcl-lang/discussions/1422

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

[Peefy]

LGTM

[coveralls]

Pull Request Test Coverage Report for Build 9987465755

Details

• 103 of 211 (48.82%) changed or added relevant lines in 5 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.2%) to 39.803%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/client/visitor.go	3	5	60.0%
pkg/downloader/downloader.go	14	22	63.64%
pkg/oci/oci.go	34	46	73.91%
pkg/downloader/credential.go	0	27	0.0%
pkg/client/client.go	52	111	46.85%

Totals
Change from base Build 9970449927:	0.2%
Covered Lines:	3029
Relevant Lines:	7610

---

💛 - Coveralls