Use maximum allowed response size for request/response protocols (#5753)

# Description

Adjust the PoV response size to the default values used in the
substrate.
Fixes https://github.com/paritytech/polkadot-sdk/issues/5503

## Integration

The changes shouldn't impact downstream projects since we are only
increasing the limit.

## Review Notes

You can't see it from the changes, but it affects all protocols that use
the `POV_RESPONSE_SIZE` constant.
- Protocol::ChunkFetchingV1
- Protocol::ChunkFetchingV2
- Protocol::CollationFetchingV1
- Protocol::CollationFetchingV2
- Protocol::PoVFetchingV1
- Protocol::AvailableDataFetchingV1

## Increasing timeouts


https://github.com/paritytech/polkadot-sdk/blob/fae15379

/polkadot/node/network/protocol/src/request_response/mod.rs#L126-L129

I assume the current PoV request timeout is set to 1.2s to handle 5
consecutive requests during a 6s block. This setting does not relate to
the PoV response size. I see no reason to change the current timeouts
after adjusting the response size.

However, we should consider networking speed limitations if we want to
increase the maximum PoV size to 10 MB. With the number of parallel
requests set to 10, validators will need the following networking
speeds:
- 5 MB PoV: at least 42 MB/s, ideally 50 MB/s.  
- 10 MB PoV: at least 84 MB/s, ideally 100 MB/s.

The current required speed of 50 MB/s aligns with the 62.5 MB/s
specified [in the reference hardware
requirements](https://wiki.polkadot.network/docs/maintain-guides-how-to-validate-polkadot#reference-hardware).
Increasing the PoV size to 10 MB may require a higher networking speed.

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Co-authored-by: Andrei Sandu <[email protected]>