* all: update to master zig 0.16.x-dev
* all: use the new `arm-3ds` target
* horizon/debug: implement a proper panic handler and segfault handler
* horizon: use `Io.failing` temporarily (thanks sfiedler)
* dependencies: remove zdap (deprecated), plz parse the arguments
* tools & scripts: use plz
* horizon/heap: copy SbrkAllocator directly from master
* horizon/AddressArbiter: workaround azahar kernel emulation accuracy
* build: AssembleZpsm -> AssemblePsm
* build: *.horizon.query -> `arm-3ds`
* all: misc fixes that may not apply to anything said

* 🥀 unfortunately use a forked std to allow greater overrideability.
* horizon.Object: make it a `packed struct` instead of an `enum`
* horizon.heap: add `CommitAllocator` which is thread-safe
* horizon.tls: implement TLS variables via software TLS.
* horizon.AddressArbiter: workaround some azahar accuracy issues and add
 `Mutex` and `Parker`.
* horizon.debug: basically rewrite it, it now outputs the same info as
 the default in std but without debug info yet.
* horizon.testing: needed to override the default in std.testing
* horizon.Thread.Impl: init, overrides std.Thread
* horizon.process: init, overrides std.process
* horizon.config: fix the `Kernel` struct
* horizon.Init: yeah, we also have JUICIER main's. Replaces
 horizon.application and has less boilerplate.
* horizon.Io: init but not finished, only synchronization, debug
 output, romfs and misc things are implemented.
* horizon.Io.test: import from std
* hardware.cpu.arm11: add a `Monitor` wrapper (ldrex/strex)

ci: split CI and CD and re-enable CI on pull requests.
horizon.Io: unfortunately... use a global 😭
horizon.Init: add an `io` field
horizon.start: init global Io if juiced
gitignore: add zig-pkg

* almost all unimplemented functions return an error instead of a
 compile error