chore: bump sdk-core and protobufjs

[mjameswh]

What changed

• Bump sdk-core submodule to 18615a (note that this is NOT latest commit)
• Bump protobufjs to 7.5.5
• Fix a protobufjs' bug that was causing parse failure on latest Cloud Ops API drop due to addition of protoc-gen-openapiv2 annotations, which protobufjs doesn't support. The fix is implemented using PNPM's patch feature over protobufjs@7.5.4. An upstream ticket will be filed to request a proper fix, but this should be a reasonable solution until then.
• Fix @temporalio/proto's "runtime root patching" script to make it compatible with protobufjs 7.5.2+ (fix [Bug] Protobuf Payload Converter is broken after upgrading to protobufjs 7.5.2 #1717). See details below.

Details on the protobufjs@7.5.2 incompatibility

• protobufjs@7.5.2 added a fast-path cache in Namespace#lookup() that accesses this.root._fullyQualifiedObjects.
• The root accessor is defined as a non-enumerable getter on ReflectionObject.prototype, so it is not copied by for...in loops.
• When the patched root is imported via import * as proto from '@temporalio/proto', TypeScript's __importStar helper wraps the CJS module in a plain object by iterating own enumerable properties with for...in + hasOwnProperty.
• Because root is non-enumerable, it is skipped, the wrapper's root is undefined, and any subsequent this.root._fullyQualifiedObjects access crashes.
• Solution is to define root as an own enumerable getter ensures __importStar includes it in the wrapper, so that wrapper.root delegates back to the patched root (which has the proper _fullyQualifiedObjects map and full prototype chain).

[chris-olszewski]

What was the reasoning behind the core commit choice?