refactor: rename Spec to the Intent

[SparkYuan]

What type of PR is this?

/kind refactor

What this PR does / why we need it:

rename Spec to the Intent

Which issue(s) this PR fixes:

Fixes #

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 6901343019

Warning: This coverage report may be inaccurate.

We've detected an issue with your CI configuration that might affect the accuracy of this pull request's coverage report.
To ensure accuracy in future PRs, please see these guidelines.
A quick fix for this PR: rebase it; your next report should be accurate.

• 41 of 50 (82.0%) changed or added relevant lines in 25 files are covered.
• 7 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.02%) to 75.449%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/cmd/apply/options.go	2	3	66.67%
pkg/engine/operation/diff.go	0	1	0.0%
pkg/engine/operation/parser/spec_parser.go	0	1	0.0%
pkg/engine/runtime/terraform/tfops/workspace.go	0	1	0.0%
pkg/generator/appconfiguration/generator/monitoring/monitoring_generator.go	1	3	33.33%
pkg/cmd/spec/generator.go	3	6	50.0%

Files with Coverage Reduction	New Missed Lines	%
pkg/cmd/apply/options.go	7	72.03%

Totals
Change from base Build 6891595177:	-0.02%
Covered Lines:	6930
Relevant Lines:	9185

---

💛 - Coveralls