[Xon] Search Improvements 2.15.9

Workaround XF2.2.13 does the search beforechecking it it can save it as a cached value, which can result in a query that is massively more complex than expected being sent to elasticsearch

• This issue practically doesn't occur with stock XFES, but with additional search addons such as ElasticSearch Essentials this can generate unexpected errors

• Support tag/username autocomplete using XFES add-ons todo prefix matching on autocomplete

• Fix viewing the index list could be blocked when elasticsearch is configured but inaccessible

• Improve phrasing of custom search term on the advanced search page.
  • Change the phrase 'search only x' to 'search x only' to match XenForo.
  • Supports arbitrary phrases for 'search x only' by adding the phrase svSearchImprov_search_container.x where x is the content type. Ships with the current customizations:
    • svSearchImprov_search_container.thread: "Search titles and first posts only"
    • svSearchImprov_search_container.conversation: "Search titles and first messages only"

• During upgrades, fix " Access to undeclared static property " error.
• Do not show the "Tags will be searched" tooltip as part of "Search titles only" in advanced search for content types which do not implement tagging

• Improve how thread/tickets by others in a category without view-other permission are filtered out of search results when using XFES without ElasticSearch Essentials
• Add PermissionConstraint helper class, designed to simplify implementing XF Search handler's getTypePermissionConstraints function
• Add "Collect search DSL & debug statistics" option (Default off), designed as a developer tool and strongly not recommended for production usage.

• Cleanup add-on description & readme file
• Update XFES dependent option descriptions to include if they require XFES
• Improve styling of 'no results' search result in an overlay
• Fix search result terms do not display when search results are in an overlay
• Fix custom styling triggering "Your changes have been saved." when clicking a member search link

• Fix "Push "View X by others" option being disabled would cause some user information to not be indexed, which had the implicit "rebuild search index" if this setting was then enabled.
  • This fixed conversation search when using Conversation Improvements v2.4.x+
  • Requires a re-index of at least conversations/conversation messages to re-add the missing information.
  • For most sites, disabling the "Push "View X by others" check into XFES" option is not recommended

• Fix error "Object of class XF\Mvc\Reply\View could not be converted to string" when a user is denied search tries to use search

• Fix additional XFES index page would show even when XFES was not installed/active