refactor(vm): replace custom JSON types with standard Amino encoding (alternative to #4972)

[jaekwon]

Summary

This builds on @gfanton's PR #4972.

• Remove JSONField, JSONStructValue, JSONArrayValue, JSONMapValue, JSONMapEntry, JSONObjectInfo types from gnolang
• Use ExportValues() + amino.MarshalJSON() instead — the same encoding already used for persistence
• Make tryGetError panic-safe: re-panics OOG, gracefully degrades on other panics (omits @error field)
• Net ~960 lines removed

Follow-up PR

A separate PR for a state explorer will add:

• A vm/qtype query endpoint for fetching type definitions (including struct field names)
• A client-side JavaScript library for converting the Amino JSON into human-readable format

Test plan

• All convert_test.go tests pass (primitives, structs, slices, pointers, maps, declared types, cycles, errors)
• All keeper_test.go tests pass (persisted objects, nested object traversal, JSON formatting)
• All values_export_test.go tests pass
• Panicking .Error() gracefully omits @error field
• OOG during .Error() properly re-panics

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[codecov]

Codecov Report

❌ Patch coverage is 80.77994% with 69 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
gnovm/pkg/gnolang/values_export.go	81.74%	40 Missing and 6 partials ⚠️
gno.land/pkg/sdk/vm/convert.go	82.85%	3 Missing and 3 partials ⚠️
gno.land/pkg/sdk/vm/keeper.go	86.20%	2 Missing and 2 partials ⚠️
gnovm/pkg/gnolang/uverse.go	0.00%	4 Missing ⚠️
gno.land/pkg/sdk/vm/handler.go	90.00%	2 Missing and 1 partial ⚠️
gnovm/pkg/gnolang/alloc.go	0.00%	2 Missing ⚠️
gnovm/pkg/gnolang/values_fill.go	0.00%	2 Missing ⚠️
gnovm/pkg/gnolang/values_string.go	0.00%	2 Missing ⚠️

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[jefft0]

The PR description says "Add vm/qtype query endpoint for fetching type definitions (including struct field names)". Note that there is already the vm/qdoc endpoint which returns package information including types. For example:

gnokey query vm/qdoc -data "gno.land/p/nt/avl/v0" -remote https://rpc.gno.land:443

This includes the type information for the Node struct:

    {
      "name": "Node",
      "type": "struct {\n\tkey       string // key is the unique identifier for the node.\n\tvalue     any    // value is the data stored in the node.\n\theight    int8   // height is the height of the node in the tree.\n\tsize      int    // size is the number of nodes in the subtree rooted at this node.\n\tleftNode  *Node  // leftNode is the left child of the node.\n\trightNode *Node  // rightNode is the right child of the node.\n}",
      "doc": "Node represents a node in an AVL tree.\n",
      "alias": false,
      "kind": "struct",
      "fields": [
        {
          "name": "key",
          "type": "string",
          "doc": "// key is the unique identifier for the node.\n"
        },
        {
          "name": "value",
          "type": "any",
          "doc": "// value is the data stored in the node.\n"
        },
        {
          "name": "height",
          "type": "int8",
          "doc": "// height is the height of the node in the tree.\n"
        },
        {
          "name": "size",
          "type": "int",
          "doc": "// size is the number of nodes in the subtree rooted at this node.\n"
        },
        {
          "name": "leftNode",
          "type": "*Node",
          "doc": "// leftNode is the left child of the node.\n"
        },
        {
          "name": "rightNode",
          "type": "*Node",
          "doc": "// rightNode is the right child of the node.\n"
        }
      ]
    }

[moul]

It seems like a good idea to test against the entire reply rather than checking for substrings. (whole file)

[moul]

c73c0fb

[jaekwon]

please push

[jaekwon]

@gfanton ok. lets keep both for now but migrate over time to orthogonal APIs.

qdocs returning types is not orthogonal (it's composite) because well, a package doc isn't doc about any type, it's about names. So really qdoc should change to not return type information, and qtypes should be called separately to get type information without docs.

For now this is what we need for #5283 (new state explorer) MVP. I don't think the state explorer should be showing docs though.

For JS library UX the misc/gnojs javascript library is where we can make composite APIs built upon the orthogonal APIs.