chore: add latest referenceTimestamp to OTC interface (#1454)

**Motivation:**

We want to add `latestReferenceTimestamp` to the interface. 

**Modifications:**

- Add `getLatestReferenceTimestamp` to OTC interface
- On initialization, update the `latestReferenceTimestamp` so that the
first global table root update can use the already set reference
timestamp
- Make bindings

**Result:**

Easier offchain integration

Author: ypatil12