Add additional field number allocations for ygot. (#11518)

```
* (M) docs/options.md
  - Add two addition field options that are used as markers for
    specific YANG types in generated protobufs.
```

This adds two additional unique `FieldOptions` field numbers for annotat YANG leaf-lists, and leaf-lists of unions that need specific handling in field option code. Definitions for these fields are in github.com/openconfig/ygygot, particularly https://github.com/openconfig/ygot/blob/master/proto/yext/yext.proto.

Closes #11518

COPYBARA_INTEGRATE_REVIEW=https://github.com/protocolbuffers/protobuf/pull/11518 from robshakir:main ea73e697e7fe4ba3bcb864d5c09d8ae1f25976f6
PiperOrigin-RevId: 502245756