sp_BlitzLock - fix duplicate plans

[Tisit]

Fix for #3765 (or at least improvements)

Turns out there are many causes of this:

• if there are many statements in procedure we need to use specific statement start and end columns, otherwise we get something close to cartesian join
• We may get duplicate query plans in #deadlock_results -> I take just max query_xml and group by rest of the columns. Seemed easiest way to fix for me
• one query can have deadlock on many different tables. This caused same SQL to be reported many times. At least that is my interpretation, because removing dow.object_name on line 4145 (which was unused anyway) and aggregating seemed to fix this particular problem.

In the environment where I saw all these problems the number of rows returned dropped from 10k+ to 60. Much more managable in my opinion.

Thanks