feat: allow kcl import to load http/https urls

[Arpit529Srivastava]

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

• N
• Y

fix: #296

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

• pkg/fs/util.go
• pkg/options/import.go
• cmd/kcl/commands/import.go

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

Allows kcl import to accept HTTP/HTTPS URLs as input, enabling direct import from remote sources without manual download.
eg:

kcl import -m json https://api.github.com/meta

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

# Test URL import
kcl import -m json https://api.github.com/meta -o test.k

# Verify local files still work
kcl import data.json

[Arpit529Srivastava]

/cc @Peefy PTAL
Thank you

[coveralls]

Pull Request Test Coverage Report for Build 20691291062

Details

• 0 of 62 (0.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-2.0%) to 27.386%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/options/import.go	0	24	0.0%
pkg/fs/util.go	0	38	0.0%

Totals
Change from base Build 20614186533:	-2.0%
Covered Lines:	241
Relevant Lines:	880

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💛 - Coveralls