Change sysprof build option default value to 'auto'

Now sysprof can be enabled by default in distros that use
-Dauto_features=enabled or for developers who already have sysprof
installed, while it's still disabled for developers who do not have
sysprof installed. See #3354

meson_options.txt

@@ -68,7 +68,7 @@ option('tapset_install_dir',
 
 option('sysprof',
        type : 'feature',
-       value : 'disabled',
+       value : 'auto',
        description : 'include tracing support for sysprof')
 
 option('documentation',