Fix: order a provider call without $params after the calls it reads

[briankane]

Description of your changes

Fixes #148.

Since #141 the resolver found what a provider call depends on by following the references in its $params. A call written in the legacy style has no $params: its inputs are its own top-level fields. It was taken to depend on nothing, ran in the first level, and read another call's output before that call had run. kubevela/workflow's request step, whose legacy op.#ConditionalWait reads req.$returns, waited forever.

A call's inputs are now its $params, or for a legacy call each of its top-level fields, hidden ones included. The fields rather than the call's own expression: that expression is the conjunction with the definition the call is made from, and following it reaches into the package the definition lives in. kubevela/workflow's legacy op package declares NoExist: _|_ at the top level, and reading through it both lost the dependency and left the reread call bottom (explicit error (_|_ literal) in source).

paramsResolved is unchanged in behaviour: a call with no $params has nothing to check there, since a legacy call's top-level fields hold its outputs as well as its inputs.

How has this code been tested

• TestLegacyCallWaitsForTheCallItReads: a legacy call reading a new-style call's $returns (workflow's request), and a legacy call reading another legacy call's output (workflow's apply-job). A third case reads its input through a hidden field. Each fixture puts the reader before what it reads, so traversal order alone cannot pass it, and the test package declares a top-level NoExist: _|_, as workflow's legacy op package does. Fails on main and at cue/cuex: resolve a template's provider calls in batches, not one walk each #141; passes at fix: drop empty path and unrenderable value from function call errors #140 and with this change.
• All pkg packages pass, including cue/cuex: resolve a template's provider calls in batches, not one walk each #141's equivalence, corpus and fidelity suites.
• kubevela/workflow built against this branch: the real request step template through its task loader now succeeds (on main it stays running/Wait), and its unit and envtest suites pass apart from the provider tests that also fail locally on main (macOS port and patching issues).

Special notes for your reviewer

• Feat: forEach, repeating a workflow step once per item workflow#261 is the first PR to bump kubevela/pkg past cue/cuex: resolve a template's provider calls in batches, not one walk each #141, and its e2e spec for the request step fails until this lands.
• Not changed here, and not investigated: workflow's legacy op package also declares a top-level context: _, and with it removed the legacy wait does not run at all. It is not needed for this fix.

[codecov]

Codecov Report

❌ Patch coverage is 90.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 92.40%. Comparing base (80dd365) to head (7a4e419).

Files with missing lines	Patch %	Lines
cue/cuex/compiler.go	90.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #149      +/-   ##
==========================================
+ Coverage   92.37%   92.40%   +0.02%     
==========================================
  Files         114      114              
  Lines        6653     6659       +6     
==========================================
+ Hits         6146     6153       +7     
+ Misses        507      506       -1     

Flag	Coverage Δ
unit-test	92.40% <90.00%> (+0.02%)	⬆️

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[cubic-dev-ai]

All reported issues were addressed across 2 files

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[cubic-dev-ai]

All reported issues were addressed across 1 file (changes from recent commits).

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Fix all with cubic | Turn on auto-fix | Re-trigger cubic</sub>