Progress toward structured lock checks

This change replaces the old array-of-arrays with an array of structs
that have a pointer to the register array.  The struct will soon also
hold the additional data required to perform structured lock checks,
which confirm that every monitor-enter instruction is paired with
a monitor-exit.  (Prototype fields have been added but are currently
unused.)

No change in behavior is expected, although verification of the
bootstrap classes does take about 5% longer now.

Bug 2534655

Change-Id: Idf25f9a72c5e6cdefe201eebe7c3f5a37064ffca