The current profiling mode (called kLeafNodeLineNumbers in this CL)
produces a tree, with each node representing a stack frame that is seen
in one or more samples taken during profiling. These nodes refer to a
particular function in a stack trace, but not to a particular line or
callsite within that function.

This CL adds a new more (called kCallerLineNumbers) which produces a
different profile tree, where each stack trace seen during profiling,
including the line number, has a unique path in the tree.

The profile tree was previously keyed on CodeEntry*. Now it is keyed on
the pair of CodeEntry* and line_number, meaning it has distinct nodes
for those combinations which exist, and each distinct stack trace that
was sampled is represented in the tree.

For optimized code where we have inline frames, there are no line
numbers for the inline frames in the stack trace, causing duplicate
branches in the tree with kNoLineNumberInfo as the reported line number.
This will be addressed in follow-ups.

Bug: v8:7018
Cq-Include-Trybots: luci.chromium.try:linux_chromium_rel_ng
Change-Id: I512e221508f5b50ec028306d212263b514a9fb24
Reviewed-on: https://chromium-review.googlesource.com/1013493
Commit-Queue: Peter Marshall <petermarshall@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53298}