MultiServer: speed up location commands (#1926)

* MultiServer: speed up location commands

Adds optimized pure python wrapper around locations dict
Adds optimized cython implementation of the wrapper, saving cpu time and 80% memory use

* Speedups: auto-build on import and build during setup

* Speedups: add requirements

* CI: don't break with build_ext

* Speedups: use C++ compiler for pyximport

* Speedups: cleanup and more validation

* Speedups: add tests for LocationStore

* Setup: delete temp in-place build modules

* Speedups: more tests and safer indices

The change has no security implications, but ensures that entries[IndexEntry.start] is always valid.

* Speedups: add cython3 compatibility

* Speedups: remove unused import

* Speedups: reformat

* Speedup: fix empty set in test

* Speedups: use regular dict in Locations.get_for_player

* CI: run unittests with beta cython

now with 2x nicer names

.gitignore

@@ -168,6 +168,10 @@ dmypy.json
 # Cython debug symbols
 cython_debug/
 
+# Cython intermediates
+_speedups.cpp
+_speedups.html
+
 # minecraft server stuff
 jdk*/
 minecraft*/