fix: lib/sh/util.sh: need `function` before functions that have an alias with the same name

lib/sh/util.sh: log!(): use new log:()

lib/sh/util.sh: added log:(), which sets an explicit log_level. this also simplifies log+().

lib/sh/util.sh: log+(): set log_level before PS4 so that the PS4 expr doesn't also need to add to log_level

lib/sh/util.sh: removed no longer needed log+ alias (which had been renamed from clog+)

lib/sh/util.sh: clog*: renamed to log* for clarity (possible now that log* is no longer used for function-local log_level setting)

: local setting of log_level: use log_local instead of relying on the log aliases, so that these aliases can instead be used for wrapping commands (the more common use case)

bugfix: lib/sh/util.sh: verbosity_compat alias: need to use `declare verbosity="$verbosity"` instead of `declare verbosity`, which would just clear $verbosity

bugfix: lib/sh/util.sh: verbosity_min alias: need to use `declare verbosity="$verbosity"` instead of log_local now that verbosity is not one of the vars changed by log++

lib/sh/util.sh: log+(): use easier-to-understand log_local instead of prefix-assignments to limit assignments to the invoked command