Problems in a prior `Payload` PR

**Describe the bug**
There are some fundamental problems found in the Payload implementation.

1. Referring to [this](https://github.com/asyml/forte/pull/828#discussion_r913377790)
a. The design requirement is to make `Payload` system generatable, but we cannot refer the generated code back in our source code. Creating this import cycle ourselves will simply create problems.
b. We discuss that if we don't have anything special methods for `TextPayload`, then we shouldn't add them into `top.py`. But if we need to have them there then we should.
2. Some conversations in the PR are not resolved, make sure to resolve all conversations before merging.
3. Let's not use [`todo`](https://github.com/asyml/forte/pull/828/files#diff-b74f73aea0aeb3c17371323001cb91e0ab0001e961f610e90184f5905c636dfcR1352), if we don't track them in issues they will sit there forever.