max rent epoch serialization

[jordy25519]

Problem

in the wild RPC providers (some) are returning account 'rentEpoch' as 18446744073709552000
there are multiple bug reports on various clients where deserialization is broken but the client libs switched to a big int to accommodate this

the solana-client crate can't parse this value currently as it exceeds u64.

invalid type: floating point 1.8446744073709552e19, expected u64

example issues caused by this:
go client issue: gagliardetto/solana-go#172 (solved with BigInt)
rust client issue:: regolith-labs/ore#26 (unsolved)

Proposed Solution

Make it clear for solana protocol that maximum rent epoch should never be serialized as anything other than 18446744073709551615

otherwise accept the situation, then solana-client rpc needs special case deserialization to handle the above value