Change zebrad-hash-lookup script so it can use zcashd or zebrad

[oxarbitrage]

Currently, the zebrad-hash-lookup bash script can only be used with zcashd as the backend as it uses the getblockheader RPC call to get information.

The call is not supported in zebrad.

This was reported by @dismad in discord, a workaround was given:

zcash-cli getbestblockhash | xargs zcash-cli getblock | jq .tx.[0] | xargs -n1 ./txDetails.sh | jq .height  workaround for now 😄

Either:

• Implement the workaround to the script
• Implement getblockheaders rpc method into zebra. Additional reasons might be wanted to do this.

[mpguerra]

We should implement getblockheader as part of zcashd deprecation. Closing as duplicate of #8442