fix: add stack depth accounting to rawEquals

[prasanna8585]

Problem

rawEquals in builtins.go, which implements jsonnet's == and != operators, recurses natively via the Go call stack when comparing nested arrays or objects. It has no stack-depth accounting anywhere in the call chain.

A self-referential jsonnet value compared with ==:

{a: $} == {a: $}

causes rawEquals to recurse into itself indefinitely, consuming memory until the process is killed by the OS (OOM) or the Go runtime's stack limit is hit.

Precedent

This is the same bug class already fixed in builtinManifestJSONEx, builtinManifestYamlDoc, and builtinManifestTomlEx (depth-counter pattern seeded from i.stack.limit, decremented per recursive call, erroring with "max manifest depth exceeded"). rawEquals was never covered by that sweep and remains vulnerable to the identical trigger pattern.

Fix

Adds a depth int parameter to rawEquals, seeded from i.stack.limit (the interpreter's own configured stack limit, default 500) at all 5 entry points, and decremented on each of the 2 recursive call sites (array element comparison, object field comparison). Errors with "max equality depth exceeded, possible infinite recursion" when exhausted — matching the existing manifest-builtin error message style exactly.

Testing

Verified with {a: $} == {a: $} — with the fix, this now returns a clean error instead of hanging indefinitely with unbounded memory growth.

[prasanna8585]

Hi @johnbartholomew @rohitjangid,

Just checking in to see if you've had a chance to look at the patch strategy for this. I'm happy to spin up the code changes for the fix in a private fork if that helps speed things up.

Thanks again for your time!