Proto J: backport !4999

Context

git cherry-pick dceb84d3f6c62787eb9ff6ba7b7e9afb6dc9d059

The description of the original MR should provide the necessary context. I reproduce it here for reference.

The size of the inbox is the sum of the size (in bytes) of its messages.

Early in the development of the feature, the value was arbitrarily set to 100_000 (bytes). In the final rush, it was then (less, but still) arbitrarily set to 250_000, with the idea that, as a rollup’s context grows, the size of the proof increases too, up to a point where a legitimate use of a rollup can no longer fill 250,000 bytes of messages.

Albeit true, this reasoning ended up imposing an arbitrary limit to all rollups, for no real benefit for users and the layer-1 implementation alike. Besides, during the early life of a rollup, where (1) the context is small, and (2) it is not really possible to reduce the size of the operations by using indexes. Besides, increasing the maximum size of an inbox does not change anything for the layer-1. Messages are not stored in the context, while messages that could have been rejected due to the size limit remains in the block.

As a consequence, we increase the maximum size of the limit to almost the size of a block, that is 500,000 bytes.

Manually testing the MR

Checklist

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