Feat: add vela def gen-cue command

[iyear]

Description of your changes

🤖 Generated by Copilot at 8cffb50

Summary

📝🎨✨

This pull request adds a new CLI subcommand vela def gen-cue to generate CUE schema from Go types for different kinds of definitions. It also adds a test case for the subcommand and improves the error message and the type representation in the cuegen package.

vela def gen-cue
From Go types to CUE schema
Autumn harvest time

Walkthrough

• Add vela def gen-cue command to generate CUE schema from Go types (link, link, link)

• Use cuegen and providergen packages to handle different types of definitions (link, link)
• Support custom types and output path with flags and arguments (link)
• Test the command with provider testdata and compare the output file with the expected file (link, link)

• Change Type type and constants to string values for readability and consistency (link, link)
• Import multierr package to handle multiple errors in a single value (link)

Part of #5364

Preview:

$ ./vela def gen-cue -h
Generate CUE schema from Go code.
* This command provide a way to generate CUE schema from Go code,
* Which can be used to keep consistency between Go code and CUE schema automatically.

Usage:
  vela def gen-cue [flags] SOURCE.go

Examples:
# Generate CUE schema for provider type
> vela def gen-cue -t provider /path/to/myprovider.go
# Generate CUE schema for provider type with custom types
> vela def gen-cue -t provider --types *k8s.io/apimachinery/pkg/apis/meta/v1/unstructured.Unstructured=ellipsis /path/to/myprovider.go
# Generate CUE schema for provider type with custom output path
> vela def gen-cue -t provider -o /path/to/myprovider.cue /path/to/myprovider.go


Flags:
  -h, --help                   help for gen-cue
      --nullable               Whether to generate null enum for pointer type
  -o, --output string          Output CUE file path, if not specified, the CUE file will be generated in the same directory
  -t, --type string            Type of the definition to generate. Valid types: [provider]
      --types stringToString   Special types to generate, format: <package+struct>=[any|ellipsis]. e.g. --types=*k8s.io/apimachinery/pkg/apis/meta/v1/unstructured.Unstructured=ellipsis (default [])

Global Flags:
  -y, --yes   Assume yes for all user prompts

I have:

• Read and followed KubeVela's contribution process.
• Related Docs updated properly. In a new feature or configuration option, an update to the documentation is necessary.
• Run make reviewable to ensure this PR is ready for review.
• Added backport release-x.y labels to auto-backport this PR if necessary.

How has this code been tested

Special notes for your reviewer

[iyear]

/cc @FogDong @Somefive

For other enhancements such as dry-run, multi-files, output to stdout, etc. I will list in the tracking issue and implement in other PRs.

[codecov]

Codecov Report

Patch coverage has no change and project coverage change: +3.64 🎉

Comparison is base (e828d3c) 56.88% compared to head (9af089b) 60.53%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5956      +/-   ##
==========================================
+ Coverage   56.88%   60.53%   +3.64%     
==========================================
  Files         219      224       +5     
  Lines       30973    31187     +214     
==========================================
+ Hits        17620    18880    +1260     
+ Misses      11710    10524    -1186     
- Partials     1643     1783     +140     

Flag	Coverage Δ
core-unittests	55.80% <ø> (-0.08%)	⬇️
e2e-multicluster-test	24.69% <ø> (?)
e2etests	25.06% <ø> (-0.10%)	⬇️

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see 58 files with indirect coverage changes

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