With this commit we unify three existing PSBT channel funding
integration tests into a single one with the goal of testing all three
cases with simple taproot channels as well.
This commit adds a new itest case to check the race condition found in
issue #7401. In order to control the funding manager's state, a new dev
config for the funding manager is introduced to specify a duration we
should hold before processing remote node's channel_ready message.
A new development config, `DevConfig` is introduced in `lncfg` and will
only have effect if built with flag `integration`. This can also be
extended for future integration tests if more dev-only flags are needed.
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.
