doc: move misc services into OS Service section

Move remaining services from guides into OS services.

Signed-off-by: Anas Nashif <[email protected]>

Author: nashif

doc/kernel/index.rst

@@ -9,8 +9,10 @@ Kernel
    services/index.rst
    drivers/index.rst
    usermode/index.rst
+   libc/index.rst
    memory_management/index.rst
    data_structures/index.rst
    timing_functions/index.rst
    timeutil.rst
    util/index.rst
+   iterable_sections/index.rst

doc/reference/iterable_sections/index.rst renamed to doc/kernel/iterable_sections/index.rst

@@ -20,3 +20,5 @@ OS Services
    shell/index.rst
    settings/index.rst
    smf/index.rst
+   storage/index.rst
+   task_wdt/index.rst