Add rc.entries and rc.fromEntries custom operators (#4062)

### Checklist
- [x] If applicable, unit tests
- [ ] If applicable, create follow-up issues for `purchases-ios` and
hybrids

### Motivation
Port of RevenueCat/purchases-ios#7435. JSON Logic iteration operators
only accept arrays, so there is no way to filter or rebuild a keyed
object — subscriptions or entitlements maps — inside a predicate.

### Description
- Add `rc.entries`: objects become `[key, value]` pairs sorted
lexicographically by key, arrays become string-index pairs. Every other
type, strings included, throws a type mismatch, so a rule aimed at the
wrong field fails loudly instead of iterating characters.
- Add `rc.fromEntries`: the inverse, last-wins on duplicate keys.
Non-array arguments and entries that are not two-element pairs throw
rather than producing a partial object.
- Eighteen fixtures copied byte-for-byte from iOS (415 total).

### Notes
The iOS PR is still in review, so its fixtures could still change; this
file must be re-synced if they do.

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Medium Risk**
> New rule-evaluation operators can change which server-side predicates
match on keyed customer data; behavior is cross-SDK aligned and heavily
fixture-tested, with explicit type errors to avoid silent wrong matches.
> 
> **Overview**
> Adds **`rc.entries`** and **`rc.fromEntries`** to the JSON Logic rules
engine so predicates can turn keyed maps (e.g. subscriptions) into
`[key, value]` pair arrays for `filter` / `some` / `reduce`, then
rebuild objects afterward.
> 
> **`rc.entries`** emits lexicographically sorted pairs for objects and
string-index pairs for arrays; scalars (including strings) raise
**`TypeMismatch`** instead of behaving like JS `Object.entries`.
**`rc.fromEntries`** reverses valid two-element pair lists with
last-wins duplicate keys and strict validation—malformed or partial
entries throw rather than producing a trimmed object.
> 
> Dispatch is registered in **`CustomOperators`**, with **18**
conformance fixtures in **`rc_entries.json`** and the global fixture
count bumped to **519**.
> 
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
499f18d02b393ddc10d8072b1e3eb18e0bbb705e. Bugbot is set up for automated
code reviews on this repo. Configure
[here](https://www.cursor.com/dashboard/bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Co-authored-by: Cursor <cursoragent@cursor.com>