Prevent ptrace of logd on user builds

system/core commit 6a70ded7bfa8914aaa3dc25630ff2713ae893f80 (later
amended by 107e29ac1b1c297a0d4ee35c4978e79f47013e2c indicated that logd
doesn't want it's memory accessible by anyone else. Unfortunately,
setting DUMPABLE isn't sufficient against a root level process such with
ptrace. Only one such process exists, "debuggerd".

Block debuggerd from accessing logd's memory on user builds. Userdebug
and eng builds are unaffected.  Add a neverallow rule (compile time
assertion + CTS test) to prevent regressions.

Bug: 32450474
Test: Policy compiles.
Change-Id: Ie90850cd91846a43adaa0871d239f894a0c94d38