[lldb/test] Make "inline" tests handle multiple statements at the same location

Summary:
The test machinery translates each continuous block of "//%" comments
into a single breakpoint. If there's no code between the blocks the
breakpoints will end up at the same location in the program. When the
process stops at a breakpoint lldb correctly reports all breakpoint IDs,
but the test machinery only looks at the first one. This results in a
very dangerous situation as it means some checks can be silently
stopped.

This patch fixes that by making the test machinery iterate through all
breakpoints at a given location and execute all commands.

Reviewers: vsk, JDevlieghere

Subscribers: lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D79563