The `LOG_BACKEND_FORMAT_TIMESTAMP` Kconfig currently depends on
a list of hardcoded backends.
Let's modify it to depend on an intermediary Kconfig
`LOG_BACKEND_SUPPORTS_FORMAT_TIMESTAMP` instead, which can be
selected by a OOT log backend.
Updated all exisitng supported backends to select this new
Kconfig.
Signed-off-by: Yong Cong Sin <ycsin@meta.com>
This is mainly to reduce clutter in `subsys/logging`, but also to make
backend management slightly easier.
Signed-off-by: Christopher Friedt <cfriedt@fb.com>