tp: split systrace trace parser into pieces

This is necessary for the upcoming work to parse system events from JSON
traces. The JSON code will use the line parser and tokenizer without
needing to use the trace parser.

This is a pure refactor without any functional changes.

Bug: 150213213
Change-Id: Idfd64b869f87be4922dd77781d0822e43b633a09
diff --git a/Android.bp b/Android.bp
index 4d4e23d..36dfe0c 100644
--- a/Android.bp
+++ b/Android.bp
@@ -6305,6 +6305,8 @@
     "src/trace_processor/importers/proto/system_probes_module.cc",
     "src/trace_processor/importers/proto/system_probes_parser.cc",
     "src/trace_processor/importers/proto/vulkan_memory_tracker.cc",
+    "src/trace_processor/importers/systrace/systrace_line_parser.cc",
+    "src/trace_processor/importers/systrace/systrace_line_tokenizer.cc",
     "src/trace_processor/importers/systrace/systrace_parser.cc",
     "src/trace_processor/importers/systrace/systrace_trace_parser.cc",
     "src/trace_processor/syscall_tracker.cc",