[stdlib]: Add a generic critical path graph module

This brings us closer to productionizing and generalizing
the critical path algorithm. Still in experimental until the API
is fully fledged.

2 functions extracted out:
1. _critical_path(graph_table, root_table)
2. _critical_path_intervals(graph_table, root_table, interval_table)

The first works completely in id space, the second 'flattens' for the UI

Change-Id: I04130e421eb7ccdb43965fccc01e809c6afbae61
diff --git a/Android.bp b/Android.bp
index 11c9b2a..279cfe9 100644
--- a/Android.bp
+++ b/Android.bp
@@ -13163,6 +13163,7 @@
         "src/trace_processor/perfetto_sql/stdlib/deprecated/v42/common/slices.sql",
         "src/trace_processor/perfetto_sql/stdlib/deprecated/v42/common/timestamps.sql",
         "src/trace_processor/perfetto_sql/stdlib/export/to_firefox_profile.sql",
+        "src/trace_processor/perfetto_sql/stdlib/graphs/critical_path.sql",
         "src/trace_processor/perfetto_sql/stdlib/graphs/dominator_tree.sql",
         "src/trace_processor/perfetto_sql/stdlib/graphs/partition.sql",
         "src/trace_processor/perfetto_sql/stdlib/graphs/scan.sql",