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?

WebApplet crashes on exit with 16 more MB stolen, apparently.

* result: try out some experimental shenanigans

* result: sketch out some more shenanigans

* result: see what it looks like to convert kernel to use result conds instead of guards

* make rest of kernel use experimental new macro-ing

* Work around Clang's incomplete C++20 support for omitting typename

* vapours: fix Clang error about missing return in constexpr function

* stratosphere: fix call to non-constexpr strlen in constexpr function

strlen being constexpr is a non-compliant GCC extension; Clang
explicitly rejects it: https://reviews.llvm.org/D23692

* stratosphere: add a bunch of missing override specifiers

* stratosphere: work around Clang consteval bug

Minimal example: https://godbolt.org/z/MoM64v93M

The issue seems to be that Clang does not consider f(x) to be a
constant expression if x comes from a template argument that isn't
a non-type auto template argument (???)

We can work around this by relaxing GetMessageHeaderForCheck (by using
constexpr instead of consteval). This produces no functional changes
because the result of GetMessageHeaderForCheck() is assigned to a
constexpr variable, so the result is guaranteed to be computed
at compile-time.

* stratosphere: fix missing require clauses in definitions

GCC not requiring the require clauses to be repeated for member
definitions is actually a compiler bug:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96830

Clang rejects declarations with missing require clauses.

* Fix ALWAYS_INLINE_LAMBDA and parameter list relative order

While GCC doesn't seem to care about the position of the always_inline
attribute relative to the parameter list, Clang is very picky
and requires the attribute to appear after the parameter list
(and before a trailing return type)

* stratosphere: fix static constexpr member variable with incomplete type

GCC accepts this for some reason (because of the lambda?) but Clang
correctly rejects this.