xF2 Add-on Slow query logger 2.2.1

• Fix various numerical admincp options which did not step in the incremental values as intended, while allowing arbitrary values in the range to be entered

• Require XenForo 2.2+
• Require php 7.2+
• Fix infinite recussion which could result in segfaults when the caching backend is empty and fetching XF options triggers a database query
• Prune stacktrace from sql query logs once >150 queries are collected, and be more aggressive about flipping LogSimpleOnly flag
• Only collect stack-traces if the _debug flag is present in the request

• Require php 7+
• Update add-on options to have their own additional input-group and to be better formatted
• Add "Too many queries threshold" option to help detect N+1 query behaviour. With various options to skip possible false positives.