feat: update init cmd

[liu-hm19]

What type of PR is this?

/kind feature

What this PR does / why we need it:

This PR updates the kusion init command.

Which issue(s) this PR fixes:

Fixes #781 #783 #810 #820

Special notes for your reviewer:

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 8320929558

Details

• 105 of 117 (89.74%) changed or added relevant lines in 5 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.8%) to 73.54%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/scaffold/demo_loader.go	46	58	79.31%
<!--	Total:	105	117

Totals
Change from base Build 8320805186:	0.8%
Covered Lines:	6726
Relevant Lines:	9146

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💛 - Coveralls