liblog: event log list logging handler

(cherry pick from commit bd1ad049)

Based off an initial request and effort by williamluh@google.com

- Added the following functions:

* Composing and Writing:

android_log_context create_android_logger(uint32_t tag)

int android_log_write_list_begin(android_log_context ctx)
int android_log_write_list_end(android_log_context ctx)

int android_log_write_int32(android_log_context ctx, int32_t value)
int android_log_write_int64(android_log_context ctx, int64_t value)
int android_log_write_string8(android_log_context ctx, const char *value)
int android_log_write_float32(android_log_context ctx, float value)

int android_log_write_list(android_log_context ctx, log_id_t id)

* Reading and Interpreting:

android_log_context create_android_log_parser(const char *msg, size_t len)

android_log_list_element android_log_read_next(android_log_context ctx)
android_log_list_element android_log_peek_next(android_log_context ctx)

* Destroy context used above:

int android_log_destroy(android_log_context *ctx);

- Added unit gTests

We moved implemented android_log_buffer_to_string() to the test since
it is an alternate for already existing logprint functionality.
Please move into liblog should it be of some common use, otherwise
as is it is a good means of stessing the reading and interpreting
handlers.

Signed-off-by: Mark Salyzyn <salyzyn@google.com>
Bug: 19235719
Change-Id: I4aa1927e8e6a75f0a129d15a27c891cf1ccd4f5c