Clang: On the road to update and preprocessor support

This patch has grown in a quite big change set and it is really hard to
divide it in different parts.
V2::ProjectPartContainer is now using FileIds instead of file paths. This
cleans code up because it is a big step in the direction that internally
only file ids are used. But it is depending on the file cache, so the
file cache has to be provided as an argument. There is now an interface for
transactions too which are ease the testing of them and enables the support
of preprocessor. It adds macros as symbols and is saving used macros. The
used macro support is enabling update improvements because only if a
changed macro is used it needs to be recompiled. This is still in flux
and can be changed in later patches.

Change-Id: I492a2c9af1201d40fdd9f46a0045f7878bbbaa3d
Reviewed-by: Ivan Donchevskii <ivan.donchevskii@qt.io>

src/libs/sqlite/sqlitedatabase.cpp

@@ -116,7 +116,7 @@ void Database::execute(Utils::SmallStringView sqlStatement)
 
 void Database::initializeTables()
 {
-    ImmediateTransaction<Database> transaction(*this);
+    ImmediateTransaction transaction(*this);
 
     for (Table &table : m_sqliteTables)
         table.initialize(*this);