audioflinger: Fix thread fields locking for dumps

Previously, ThreadBase::mLock was only acquired inside
ThreadBase::dumpBase method. That means, dumping of fields of
descendant classes, tracks, and effect chains was performed
without holding ThreadBase::mLock.

This patch changes the way of how dumping is driven. Now only
ThreadBase has a public 'dump' method which is non-virtual.
This method takes the lock and dumps all the fields, tracks, and
effect chains. It calls virtual methods for dumping the contents
of descendant classes.

Bug: 118842894
Test: compare audioflinger dumps A/B
Change-Id: Iaafc75d13935a6a92ca37f9567b7ac7c31374b3e