IWYU: Fix some missing includes

Breakdown:

```
src/cts/src/TechChar.cpp:                #include "sta/StringUtil.hh" for sta::StringSeq
src/drt/test/gcTest.cpp:                 #include "db/obj/frNet.h" for drt::frNet
src/rsz/src/MoveTracker.cc:              #include <map> for std::map
src/rsz/src/MoveTracker.cc:              #include <vector> for std::vector
src/web/src/timing_report.cpp:           #include "sta/StringUtil.hh" for sta::StringSeq
```

Signed-off-by: Henner Zeller <h.zeller@acm.org>

Author: hzeller

src/cts/src/TechChar.cpp

@@ -32,6 +32,7 @@
 #include "sta/Sdc.hh"
 #include "sta/Search.hh"
 #include "sta/SearchClass.hh"
+#include "sta/StringUtil.hh"
 #include "sta/TableModel.hh"
 #include "sta/TimingArc.hh"
 #include "sta/TimingModel.hh"

src/drt/test/gcTest.cpp

@@ -9,6 +9,7 @@
 #include <vector>
 
 #include "db/obj/frMarker.h"
+#include "db/obj/frNet.h"
 #include "db/tech/frConstraint.h"
 #include "db/tech/frViaDef.h"
 #include "fixture.h"

src/odb/include/odb/dbObject.h

@@ -32,7 +32,6 @@ class _dbObject;
 ///
 enum dbObjectType
 {
-
   // Design Objects
   dbGdsLibObj,
   dbBlockObj,

src/rsz/src/MoveTracker.cc

@@ -9,10 +9,12 @@
 #include <iomanip>
 #include <ios>
 #include <limits>
+#include <map>
 #include <sstream>
 #include <string>
 #include <tuple>
 #include <utility>
+#include <vector>
 
 #include "db_sta/dbNetwork.hh"
 #include "odb/db.h"

src/web/src/timing_report.cpp

@@ -31,6 +31,7 @@
 #include "sta/Search.hh"
 #include "sta/SearchClass.hh"
 #include "sta/Sta.hh"
+#include "sta/StringUtil.hh"
 #include "sta/Units.hh"
 #include "sta/VisitPathEnds.hh"