Fixed #22058 -- Refactored handlers and added a generic mechanism to deal with client and server errors.

**What is done**:

- Refactored handlers into generic ones.
- Deprecated original default views.
- Added generic views.

**Improvements Required**:
- Docs build have several warnings due to removing original handlers.
- A writeup for new views.

**Suggestions**:
- We could add two generic exceptions also: `HttpClientException` and `HttpServerException` to add onto the functionality.

@timgraham 
Will do that.
Btw because we are no longer having `handler400/404/403/500`, so there are several problems in the docs especially in `deprecation.txt` and `release_notes` where these are linked.
Any suggestions on how to avoid that.