Database debug log cleanup (remove wgDebugDumpSqlLength/wgDebugDBTransactions)

Database debug log cleanup (remove wgDebugDumpSqlLength/wgDebugDBTransactions)

* Simplify the debug log call and use queries group
* Remove $wgDebugDumpSqlLength, as profiler output
  already has shortened query strings (one can use
  profiling without DBO_DEBUG)
* Removed $wgDebugDBTransactions as BEGIN/COMMIT already show
* Removed PostgresTransactionState as it was only used for
  $wgDebugDBTransactions handling
* This cuts down on lots of global variable usage

Change-Id: I185adb1694441d074dea965960429b4910727620