LPv2: Fix weights with batch messages

[lemunozm]

Description

• Add max_processing_weight() method to MessageProcessor that allows to know upfront the worst case for processing a message.
• Check the worst case before processing.
• Adapt weight to work fine with batches

TODOS

• [x] This should be merged first: https://github.com/centrifuge/centrifuge-chain/pull/1949
• [x] We need to add on_idle tests for the event pallet. Will do it in this PR later

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 76.00000% with 6 lines in your changes missing coverage. Please review.

Project coverage is 47.97%. Comparing base (4bfeabe) to head (cac1931).

Files	Patch %	Lines
pallets/liquidity-pools-gateway/src/lib.rs	28.57%	5 Missing :warning:
pallets/liquidity-pools-gateway/queue/src/lib.rs	92.30%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1951 +/- ## ========================================== + Coverage 47.83% 47.97% +0.14% ========================================== Files 183 183 Lines 12904 12908 +4 ========================================== + Hits 6172 6192 +20 + Misses 6732 6716 -16 ```

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[lemunozm]

You should not be too many, because the parts I modify you don't 🤞🏻. @wischli tell me if you have some comments regarding this post-mortem, to merge this ASAP for @cdamian