v1.27.6

Features:
Update on most navmeshes with jumplinks and smaller navs (Navs#7)

Fixes:
Add is IsValidPlayer() check (Mods#855)
Fix PlayerInventory_TakeAllInventoryItems not being threaded (Mods#852)
Fix typo in README to match actual folder structure (Mods#857)

Refactoring:
core: Remove uses of Autohook from filesystem.cpp (Launcher#795)
core: Remove uses of Autohook from hooks.cpp (Launcher#796)
client: Remove uses of Autohook from latencyflex.cpp (Launcher#789)
client: Remove uses of Autohook from languagehooks.cpp (Launcher#787)
core: Remove uses of Autohook from sourceinterface.cpp (Launcher#798)
engine: Remove uses of Autohook from gl_matsysiface.cpp (Launcher#801)
core: Remove use of SourceInterface for CCvar (Launcher#804)
logging: Remove use of SourceInterface for CGameConsole (Launcher#803)
vscript: Move squirrel types to their respective files (Launcher#788)

Contributors:
@ASpoonPlaysGames @F1F7Y @hummusbird @x3Karma @Zanieon