[catnap] Move states and YielderHandle allocation into CatnapQueue

[iyzhang]

This PR moves the Catnap libOS towards our eventual architecture. There are a few important steps that this PR implements:

1. The CatnapLibOS now only contains cross-queue functionality and no state. It is never referred to through a mutable reference.
2. All libOS level state is contained in the runtime and qtable, which will eventually move to the runtime. It is dynamically borrowed at runtime.
3. The CatnapQueue only contains single-queue functionality and no state. It is never referred to through a mutable reference.
4. All queue level state is kept in the platform-specific Socket data structure. It is dynamically borrowed at runtime.
5. All asynchronous operations are broken up into two functions at both the libOS level and the queue level: one function for synchronous functionality and another for asynchronous functionality.

After this PR the following guidelines are recommended for our architecture:

1. Never use mut on stateless objects, specifically the libOS and queue structures. We should never pass &mut self for those.
2. State should be contained in platform-specific abstractions because generally the state that needs to be kept is platform-specific. The exceptions to these are the list of pending ops per queue and the SocketStateMachine, which are shared across libOSes and platforms.
3. All functionality for every call should be divided by whether the code operates on a single queue or more than one queue. All single-queue code shall be placed in the Cat*Queue class and all multi-queue code shall be placed in the Cat*LibOS class.
4. All asynchronous calls must be further divided into synchronous operations and asynchronous operations and placed in respective functions.
5. At the libOS level, there should be no state outside of the queue table (and a platform-specific backmap of addresses to queues). This state will eventually be kept in a shared runtime. If there are exceptions, they should undergo an architectural review.
6. Only asynchronous functions can block and only if they take in a yielder. Always separate synchronous and asynchronous code into two functions.

[anandbonde]

Left a few comments.

[anandbonde]

Looks good.