Reverse displayed endianness of transaction and block hashes

[oxarbitrage]

Replaces #1056

• Cherry picked commit from @vramana where the hard work was done, hope this is ok.
• Fixed the test cases where it was failing.
• Fixed zebra-checkpoints binary.

Todo:

• Get a new checkpoint list for mainnet and testnet. This will be done by @teor2345. I think we can just push the list once done into this PR.

Should close #1031 when/if merged.

[teor2345]

We can't merge this PR yet - I still need to rebuild the full checkpoint lists.

[teor2345]

I rebuilt the checkpoint lists in commit 544c572.

[teor2345]

@oxarbitrage @yaahc I also found a few more places that needed updates:

• 9ab0670 - zebrad-hash-lookup script
• 5c91a89 - fixed hash in transaction::Hash tests
• 2476f61 - hash order comment
• cc0c198 - TransactionHash to transaction::Hash from Major zebra-chain reorg #905
  • included in this PR because it conflicts with the other transaction changes

[teor2345]

I also checked the list of tasks in #1031, and I'm running zebrad start on mainnet and testnet.

[teor2345]

I tried to test this change using zebrad start, but bugs in the sync, state, and network code prevented a full sync. See #1181, #1182, and #1183.

I still think we should merge this change, it's a low-risk improvement, and the bugs aren't likely to be related to this change.

[hdevalence]

LGTM, but did not test yet.

[vramana]

@oxarbitrage Thanks for picking up the PR. I was on vacation and couldn't find the time to finish the PR.