kern: don't allow mapping device pages as executable on abi 26.x+

kern: make KProcess layout accurate to N's code

kern: N made this an u32 for some reason

kern: write thread handle to tls +0x110 on creation

kern: eshop actually requires an extra mb

kern: fix comparison typo

kern: 21.0.0 requires an even smaller memory pool...

kern: fix debug build for [[nodiscard]] changes

kern: fix whoops introduced by nodiscard refactor

kern: exception flags are now atomic. ...

This is a really weird one, because they didn't actually update the
code which updates these flags in asm, these still use ldrb/orr/strb.
But every access to these via c++ is now an atomic ldxrb/stxrb loop.
Maybe they just forgot to update the asm?

kern: pass u32 directly to CopyMemoryToUserSize32Bit

ams: mark ams::Result [[nodiscard]] (partially complete). ...

NOTE: This work is not yet fully complete; kernel is done, but
it was taking an exceedingly long time to get through libstratosphere.
Thus, I've temporarily added -Wno-error=unused-result for libstratosphere/stratosphere.

All warnings should be fixed to do the same thing Nintendo does as relevant, but this
is taking a phenomenally long time and is not actually the most important work to do,
so it can be put off for some time to prioritize other tasks for 21.0.0 support.

kern: Nintendo now also devirtualizes KAutoObject::DynamicCast

kern: write cpu tick differential to tls +0x108 on thread switch

build: portability fixes ...

- Invoke Python scripts with `python3` if `python` is not available.

  Despite SciresM preferring Python 2, the scripts used in the build all
  worked in Python 3 already, so this is just a Makefile change.

- Export `MAKE` to work around a GNU bug.

  See the comment for details.

- `rmdir --ignore-fail-on-non-empty` -> `rmdir 2>/dev/null`

  macOS `rmdir` doesn't support `--ignore-fail-on-non-empty`.

  This is a slight downgrade in functionality, because now we ignore all
  errors from `rmdir` rather than just 'Directory not empty'.  I could
  have avoided this with a more complicated fix, but the benefit strikes
  me as not worth the complexity.  Let me know if you disagree.

- Append `$(DEVKITPRO)/tools/bin/` to `$PATH` when invoking
  `build_romfs`.

  This avoids the need to add devkitPro directories to `$PATH` when
  building Atmosphere.

  If you already have `build_romfs` in your PATH, then that will still
  take precedence.  (This seemed like the nicer option, though I don't
  have strong opinions.)

kern: move spendsgir static assert

kern: save/restore spendsgir in KInterruptController::Save/RestoreCoreLocal

kern: wait 100us after synchronizing cores before saving interrupt state on sleep

kern: use KLightLock for KCoreBarrierInterruptHandler

fs.mitm: add and use memlet module to temporarily steal applet memory while building romfs images. ...

Starting in 20.0.0, the browser needs more applet memory to function, so we can't steal as much any more.
Thus, we now steal 14 MB on 20.0.0+ instead of 40MB.

However, since this reduces memory available for custom system modules, we are adjusting to compensate.
ams.mitm's heap size has been reduced from 32MB to 12MB (recovering 20MB).
In addition, fs.mitm now uses a new mechanism for stealing memory from the applet pool while romfs is being built.

On net, we are compromising:
    * Custom sysmodules lose memory available to them.
        On 19.0.0/AMS 1.8.0, there was 30 MB available for custom sysmodules.
        Stealing 14 MB instead of 40 MB, we lose 26 MB of that. Reducing ams.mitm's usage will gain us back 20.
        Nintendo also appears to...use 4 extra MB, in 20.0.0, from my test homebrew.
        So on 20.0.0/AMS 1.9.0, there should be 20 MB available for custom sysmodules.
        On the bright side, on <20.0.0/AMS 1.9.0, I guess there will be 50 MB available for custom sysmodules now?
    * totk mods will lose the ability to...put every file in the romfs on sd card. There will be some unknown maximum filecount for totk mods.
        On the bright side, implementing the transient memory stealing should improve compatibility for some mods which strictly add files?

kern: plutoo is an intellectual, I am a fool, fix chicanery

kern: use callback to note pte updates in KPageTableImpl

kern: refactor FindFreeArea region search logic per 20.0.0 changes

kern: update instruction cache invalidation logic in KPageTableBase to reflect 20.0.0 changes

kern: reorder resource manager implementation

kern: support null resource limit in KSecureSystemResource

kern: adjust system registers during exception handling on MTE-violation or kernel address fault

kern: update UserspaceAccess functions for 20.0.0 changes

kern: update KAddressSpaceInfo to reflect 20.0.0 changes

kern: invert meaning of KTargetSystem/KSystemControl bools