This is a clone of #740, but without the amtl ke::AString lowercase which was implemented in a new version of amtl that 1.9-dev isn't pinned to. Updating this pin and moving fixes is beyond what should go in 1.9, and this fixes a annoying and user-impactful bug with reload/unloading plugins on windows.
Currently in 1.9, once a plugin is loaded into the pluginsys, they must be used with lowercase characters *only*, since pr #709 ignorantly modified their names.
```
// test.smx exists in /plugins/
sm plugins load TEST.smx // successful
sm plugins unload TEST.smx // TEST.smx not found, it's actually test.smx
```
This pr fixes that error by converting *all* lookups, not just loads.
* Make mac/win lookups lowercase'd
* Revert #709 & 81042cc
* Adjust HashPolicy implementation across sourcemod
Basically, in order to implement our own (actual) hash policy in
`PluginSys.h`, we needed to remove the blanket implementation of `hash`
that was used before. Now, each policy must implement `hash` along with
`matches` in order to be used with `NameHashSet`. While this does force
us to change every implementation of policies across the entirety of
sourcemod, it allows core to use flexible implementations of `hash`.
* Remove logic duplication
* Improve lowercase checks
