PPC: [fullcodegen] Implement operand stack depth tracking.

Port 38915ed7

Original commit message:
    This implements a mechanism to track the exact depth of the operand
    stack in full-codegen for every sub-expression visitation. So far we
    only tracked the depth at statement level, but not at expression level.
    With the introduction of do-expressions it will be possible to construct
    local control flow (i.e. break, continue and friends) that target labels
    at an arbitrary operand stack depth, making this tracking a prerequisite
    for full do-expression support.

R=mstarzinger@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=v8:4755,v8:4488
LOG=n

Review URL: https://codereview.chromium.org/1729613002

Cr-Commit-Position: refs/heads/master@{#34227}