Optionally usable early in CLI mains, devservers and scripts that log
before (or without) server.run(). Shares patch_log_config with the
server path (same log_config overrides), but installs no server-side
patches: Formatter gains an install flag gating the lifespan/error
middleware monkeypatches, and the NullHandler backdoor is skipped.
dev=None follows env.dev for the root level, True/False override it.
Pre-existing loggers survive the dictConfig (disable_existing_loggers
is set False).
LeoVasanko