Limit Soroban LedgerEntry size

[MonsieurNicolas]

Similar to what we do as a "catch all" to limit transaction size (done outside of env - stellar/stellar-core#3672 ): we need a limit (network setting) on how big any Soroban ledger entry can get:
while limits on SCVals , keys (#629) , etc should be enough, there is a possibility that we miss something (or a combination of things) and that can become a problem for the network over time.

It seems we should be able to enforce this within env, but if not, we should enforce this in the core bridge (when we convert entries into binary blobs when crossing back to C++).

[jayz22]

Resolved by stellar/stellar-core#3731.