Added gdb remote protocol tests across all qRegisterInfo responses.

Added support for gdb remote protocol capture/playback where there is a query/multiple-response
pattern.  The new playback entry supports:

- a general query command (key: next_query or query)
- an optional first-query command if that differs from the subsequent queries (key: first_query)
- an end regex for matching anything that would signify that the query/multi-response
  iteration has come to an end.  An assumption is that the end regex is not a content
  package we care about aside from ending the iteration. (key: end_regex)
- an optional 0-based index appended to the end of the query command 
  (key: append_iteration_suffix), default: False.
- a key used to collect responses from the query.  Any response from the gdb remote
  that doesn't match the end-of-iteration regex is captured in the playback context
  dictionary using the key specified.  That key will be an array, where each array
  entry is one of the responses from the query/multi-response iteration. (key: save_key).
- a runaway response value, defaulting to 10k, where if this many responses is captured,
  assume the ending condition regex is invalid, or the debug monitor is doing something
  goofy that is going to blow out memory or time. (key: runaway_response_count, default: 10000)

See the lldbgdbserverutils.MultiResponseGdbRemoteEntry class for details.

A MultiResponseGdbRemoteEntry is added by adding an element to the GdbRemoteTestSequence
(via GdbRemoteTestSequence.add_log_lines), using a dictionary, where the "type" key
is set to "multi_response", and the rest of the keys in the dictionary entry are
set to the keys documented for MultiResponseGdbRemoteEntry.

Added helper functions to add the required entry to grab all qRegisterInfo responses.
Added another helper to parse the qRegisterInfo response packets into an array of
dictionaries, where each key:value in the dictionary comes from the register info
response packet.

Added a test to verify that a generic register exists for the program counter,
frame pointer, stack pointer and cpu flags across all register info responses.

Added a test to verify that at least one register set exists across all register
info responses.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@209170 91177308-0d34-0410-b5e6-96231b3b80d8