[V2 Pipeline] Middleware manager

[horheynm]

Description

Adds ability to run middlewares for Pipeline and Operator callables

Problem

No existing way to just get the timings of each callable, add a generic manager for now, TimerManager in a separate pr

Solution

Create middleware manager and add a chain of callables to call middlewares before calling the callables

Design

Very similar to Starlette (Fastapi) middleware. Before calling the callables for Pipeline or Operator, add a "gadget" where the gadget logic is called before and after the callable.

One note is that Pipeline and Operator do not rely on the middleware. It doesnt know it exists. It is just a helper.

Usage

Check tests,

middleware = [MiddlewareSpec(ReducerMiddleware)]
middleware_manager = MiddlewareManager(middleware)
Pipeline(...,middleware_manager=middleware_manager)

Testing

Checks the functionality of middleware and middleware managers work as expected

[bfineran]

LGTM pending unresolved comment

[bfineran]

Approved - there are comments that need to be deleted however

[bfineran]

also - as discussed we need to cut down on the number of times we instantiate the actual middleware callable classes

[dsikka]

same as other PRs, could we merge in pipeline.py and make sure everything works as expected?

stale