liblogcat: add android_logcat_popen and android_logcat_system

Supply a wrapper to the logcat API that provides some analogous
functionality to popen and system libc calls with some bits of
KISS shell-like parsing for environment, quotes and error
redirection handling.

Test: gTest logcat-unit-tests
Bug: 35326290
Change-Id: I9494ce71267ad2b2bec7fcccfc7d4beddae9aea6