This commit adds a new build tag `integration` and removes the old tag
`rpctest` for clarity. Multiple unnecessary usages of `build !rpctest`
is also removed.
With go 1.17 a change to the build flags was implemented:
https://go.googlesource.com/proposal/+/master/design/draft-gobuild.md
The formatter now automatically adds the forward-compatible build tag
format and the linter checks for them, so we need to include them in our
code.
In this commit, the sweep package is extended from just tx generation to
an active sweeper that collects sweep inputs and autonomously proceeds
to publish the sweep tx after the batch window time interval has passed
without new inputs being added.
