This commit moves the constants LndInternalLockID and
DefaultLockDuration from the walletrpc package to the chanfunding
package, moves DefaultReservationTimeout from lncfg to chanfunding,
and also updates the lncli package with the new location.
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.
