tp: DBv2 - StringStorage

--------------------------------------------------------------------------------------
Benchmark                                 Time             CPU   Iterations      s/row
--------------------------------------------------------------------------------------
BM_QESliceTableNameEq/0              217875 ns       217866 ns         3172  5.93932ns
BM_QESliceTableNameEq/1                5137 ns         5136 ns       135325  140.023ps
BM_QESliceTableNameGlobNoStars/0     194511 ns       194485 ns         3534  5.30193ns
BM_QESliceTableNameGlobNoStars/1     155073 ns       155063 ns         4486  4.22721ns
BM_QESliceTableNameGlob/0            368158 ns       368087 ns         1908  10.0345ns
BM_QESliceTableNameGlob/1            300178 ns       300093 ns         2270  8.18092ns

Bug:283763282
Change-Id: Ibe760aefc8a5fc6d5b7bff097a31411168b27b6f

BUILD

diff --git a/BUILD b/BUILD
index 53a1870..a19997b 100644
--- a/BUILD
+++ b/BUILD
@@ -1324,7 +1324,10 @@
         "src/trace_processor/db/storage/numeric_storage.h",
         "src/trace_processor/db/storage/storage.cc",
         "src/trace_processor/db/storage/storage.h",
+        "src/trace_processor/db/storage/string_storage.cc",
+        "src/trace_processor/db/storage/string_storage.h",
         "src/trace_processor/db/storage/types.h",
+        "src/trace_processor/db/storage/utils.h",
     ],
 )