Scoru,wasm: test gather floppies proof generation size is bounded

Context

Part 1 of #3124 (closed). Check that proofs are within a size limit, during the gather-floppies mechanism of kernel loading.

Manually testing the MR

dune exec src/proto_alpha/lib_protocol/test/integration/main.exe \
                  -- test "^sc rollup wasm$"

Rebuilding the manifest should not change any files:

make -C manifest

# should show no changed files
git status --short

You can also manually verify the computation_kernel.wasm file by:

1. following the steps in the wasm_kernel README to build the kernel
2. Verifying that the manually-built kernel and the kernel included in this MR as the same using:

   diff <trili/kernel checkout>/computation_kernel.wasm <tezos/tezos checkout>/src/proto_alpha/lib_protocol/test/integration/wasm_kernel/computation.wasm

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR