This PR consolidates the `reqresp_pre_import_cache` into the `data_availability_checker` for the following reasons:
- the `reqresp_pre_import_cache` suffers from the same TOCTOU bug we had with `data_availability_checker` earlier, and leads to unbounded memory leak, which we have observed over the last 6 months on some nodes.
- the `reqresp_pre_import_cache` is no longer necessary, because we now hold blocks in the `data_availability_checker` for longer since (#7961), and recent blocks can be served from the DA checker.
This PR also maintains the following functionalities
- Serving pre-executed blocks over RPC, and they're now served from the `data_availability_checker` instead.
- Using the cache for de-duplicating lookup requests.
Co-Authored-By: Jimmy Chen <jchen.tc@gmail.com>
Co-Authored-By: Jimmy Chen <jimmy@sigmaprime.io>
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