Return void instead of bool for functions that cannot fail

Summary:
Return void instead of bool for functions that cannot fail:

• CBlockTreeDB::ReadReindexing(...)
• CChainState::ResetBlockFailureFlags(...)
• CTxMemPool::addUnchecked(...)
• CWallet::CommitTransaction(...)
• CWallet::LoadDestData(...)
• CWallet::LoadKeyMetadata(...)
• CWallet::LoadScriptMetadata(...)
• CWallet::LoadToWallet(...)
• CWallet::SetHDChain(...)
• CWallet::SetHDSeed(...)
• PendingWalletTx::commit(...)
• RemoveLocal(...)
• SetMinVersion(...)
• StartHTTPServer(...)
• StartRPC(...)
• TorControlConnection::Disconnect(...)

Backport of Bitcoin Core PR13774
https://github.com/bitcoin/bitcoin/pull/13774

Test Plan:

make check-all

Reviewers: Fabien, #bitcoin_abc, deadalnix, jasonbcox

Reviewed By: #bitcoin_abc, deadalnix, jasonbcox

Subscribers: jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D4179