[APPS][Connections Part 1] Add internal AST traversal helper

[sdkennedy2]

Motivation

The inline backend connection ID extractor needs an ESTree traversal helper, but using zimmerframe directly requires a temporary package patch and Jest shim because its current package exports do not support the repo's CommonJS integrity/test path. acorn-walk avoids that export issue but uses Acorn AST types, which forces casts around ESTree nodes.

Changes

Adds a small internal walkAst helper under packages/plugins/apps/src/backend/ast-parsing/ for inspect-only ESTree traversal. The helper walks all ESTree-shaped node types generically by scanning enumerable object properties and arrays for objects with a string type field, so it does not need a hardcoded visitor-key table. This works in a similar way to estree-walker and zimmerframe.

The API supports a universal _ visitor, specialized node-type visitors, and shared traversal state. It deliberately omits transformation features such as node replacement, immutable parent cloning, manual visit, ancestor paths, stop, and child-specific state threading because the current extractor only needs read-only traversal.

Example usage:

const importedNames = new Set<string>();

walkAst(program, importedNames, {
    ImportDeclaration(node, { state }) {
        if (node.source.value !== '@datadog/action-catalog/http/http') {
            return;
        }

        for (const specifier of node.specifiers) {
            state.add(specifier.local.name);
        }
    },
    CallExpression(node) {
        // Called for every CallExpression while walkAst continues traversing
        // children automatically.
    },
});

QA Instructions

Tests should pass.

Blast Radius

This PR only adds a new internal helper and tests. No existing production code consumes it yet, so runtime behavior is unchanged.

Documentation

• How to reliably make frontend production changes
• PR Description Guidelines
• Deploy steps

[sdkennedy2]

• [APPS][Connections Part 2] Extract inline backend connection IDs #349 : 2 dependent PRs (#351 , #352 )
• [APPS][Connections Part 1] Add internal AST traversal helper #350 👈 (View in Graphite)
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