logd: remove users of __android_logger_property_get_bool()

__android_logger_property_get_bool() has a clunky API and doesn't
belong in liblog, since a vast majority of liblog users will never
query this property.

Specifically
1) Replace with GetBoolProperty() when completely equivalent.
2) Remove checking if property values are 'eng' or 'svelte', since
   there's no evidence that those values were ever used.
3) Remove checking 'persist.logd.statistics' and 'ro.logd.statistics',
   since there's no evidence that those values were ever used.
4) Set ro.logd.kernel explicitly, so other processes don't need to
   replicate the defaults that logd uses.

Test: build
Change-Id: I7c37af64ba7754e839185f46da66bf077f09d9c3
diff --git a/logd/README.property b/logd/README.property
index 1d7d990..8fd7f48 100644
--- a/logd/README.property
+++ b/logd/README.property
@@ -7,8 +7,8 @@
 ro.logd.auditd.events      bool   true   selinux audit messages sent to events.
 persist.logd.security      bool   false  Enable security buffer.
 ro.organization_owned      bool   false  Override persist.logd.security to false
-ro.logd.kernel             bool+ svelte+ Enable klogd daemon
-ro.logd.statistics         bool+ svelte+ Enable logcat -S statistics.
+ro.logd.kernel             bool  svelte+ Enable klogd daemon
+logd.statistics            bool  svelte+ Enable logcat -S statistics.
 ro.debuggable              number        if not "1", logd.statistics &
                                          ro.logd.kernel default false.
 logd.logpersistd.enable    bool   auto   Safe to start logpersist daemon service
@@ -57,11 +57,8 @@
 
 NB:
 - auto - managed by /init
-- bool+ - "true", "false" and comma separated list of "eng" (forced false if
-  ro.debuggable is not "1") or "svelte" (forced false if ro.config.low_ram is
-  true).
 - svelte - see ro.config.low_ram for details.
-- svelte+ - see ro.config.low_ram and ro.debuggable for details.
+- svelte+ - If empty, default to true if `ro.config.low_ram == false && ro.debuggable == true`
 - ro - <base property> temporary override, ro.<base property> platform default.
 - persist - <base property> override, persist.<base property> platform default.
 - build - VERBOSE for native, DEBUG for jvm isLoggable, or developer option.