This converts the txscript package to use the stdaddr package instead of
dcrutil.Address as well as to support script versions.
All callers that use the package in the repository are updated
accordingly to maintain code that continues to build and work properly
as well as pass all tests. In order to achieve this, some previously
temporary address conversion code that is no longer needed is removed
from the blockchain/indexers and internal/rpcserver packages.
This is part of a series of commits to convert all packages in the
repository to make use of the new stdaddr package.
59d8db038f