add spentindex to getrawtransaction RPC results for bitcore block explorer
#3708 There are a few new `getrawtransaction` JSON result fields that the Insight block explorer depends on.
Break the circular dependency between main and txdb by:
- Moving `CBlockFileInfo` from `main.h` to `chain.h`. I think this makes
sense, as the other block-file stuff is there too.
- Moving `CDiskTxPos` from `main.h` to `txdb.h`. This type seems
specific to txdb.
- Pass a functor `insertBlockIndex` to `LoadBlockIndexGuts`. This leaves
it up to the caller how to insert block indices.
Zcash: This does not actually break the circular dependency for us yet, as we
still need to pull in bitcoin/bitcoin#7756 and bitcoin/bitcoin#7904.
1) Chainparams: Explicit CChainParams arg for main:
-AcceptBlock
-AcceptBlockHeader
-ActivateBestChain
-ConnectTip
-InitBlockIndex
-LoadExternalBlockFile
-VerifyDB parametric constructor
2) Also pickup more Params()\. in main.cpp
3) Pass nPruneAfterHeight explicitly to new FindFilesToPrune() in main.cpp
Activate turnstile on mainnet
This PR enables [ZIP209](https://github.com/zcash/zips/blob/master/zip-0209.rst) support on mainnet, to mark blocks as invalid if they would lead to a turnstile violation in the Sprout or Sapling value pools.
To test this PR, I performed the following manual tests:
1. Used RPC call `getblock` to verify the fallback Sprout value.
2. Individually changed the fallback Sprout block hash, block height and chain value, recompiling and relaunching the node, verifying that each individual change resulted in an error. When the block hash and block height are incorrect, an error is logged to debug.log `FallbackSproutValuePoolBalance(): fallback block hash is incorrect`. An incorrect chain value results in node termination with error: `void FallbackSproutValuePoolBalance(CBlockIndex*, const CChainParams&): Assertion '*pindex->nChainSproutValue == chainparams.SproutValuePoolCheckpointBalance()' failed.`
3. Ran the `Smoke Testing` described in PR #3885, on mainnet.
4. Launched zcashd with experimental feature `-developersetpoolsizezero` to manually trigger a turnstile violation in both Sprout and Sapling shielded pools. The Sprout turnstile violation occurred after launch, due to chance, when the next incoming block 520786 contained a Sprout unshielding transaction. The Sapling turnstile violation was triggered after creating a Sapling unshielding transaction.
add SpentIndex changes needed for bitcore block explorer
Addresses #3708, follow-on to #3837, note there are no tests yet (will come later with RPC interfaces).