feat: block RPC calls to get premerge blocks

[guha-rahul]

This pr supersedes #77, based on this comment to adopt a middleware route .
The list of all rpcs that have this check are

eth_getBlockByNumber
eth_getTransactionByBlockNumberAndIndex
eth_getBlockTransactionCountByNumber
eth_getUncleCountByBlockNumber
eth_getBlockReceipts
eth_getBalance
eth_getCode
eth_getStorageAt
eth_getTransactionCount
eth_getProof
eth_newFilter
eth_call
eth_callMany
eth_estimateGas
eth_feeHistory
eth_getLogs
trace_replayBlockTransactions
trace_block
trace_filter
trace_callMany
debug namespace
debug_traceBlockByNumber
debug_traceCall
debug_traceCallMany