This deletes the GLFW apprt from the Ghostty codebase.

The GLFW apprt was the original apprt used by Ghostty (well, before
Ghostty even had the concept of an "apprt" -- it was all just a single
application then). It let me iterate on the core terminal features,
rendering, etc. without bothering about the UI. It was a good way to get
started. But it has long since outlived its usefulness.

We've had a stable GTK apprt for Linux (and Windows via WSL) and a
native macOS app via libghostty for awhile now. The GLFW apprt only
remained within the tree for a few reasons:

  1. Primarily, it provided a faster feedback loop on macOS because
     building the macOS app historically required us to hop out of the
     zig build system and into Xcode, which is slow and cumbersome.

  2. It was a convenient way to narrow whether a bug was in the
     core Ghostty codebase or in the apprt itself. If a bug was in both
     the glfw and macOS app then it was likely in the core.

  3. It provided us a way on macOS to test OpenGL.

All of these reasons are no longer valid. Respectively:

  1. Our Zig build scripts now execute the `xcodebuild` CLI directly and
     can open the resulting app, stream logs, etc. This is the same
     experience we have on Linux. (Xcode has always been a dependency of
     building on macOS in general, so this is not cumbersome.)

  2. We have a healthy group of maintainers, many of which have access
     to both macOS and Linux, so we can quickly narrow down bugs
     regardless of the apprt.

  3. Our OpenGL renderer hasn't been compatible with macOS for some time
     now, so this is no longer a useful feature.

At this point, the GLFW apprt is just a burden. It adds complexity
across the board, and some people try to run Ghostty with it in the real
world and get confused when it doesn't work (it's always been lacking in
features and buggy compared to the other apprts).

So, it's time to say goodbye. Its bittersweet because it is a big part
of Ghostty's history, but we've grown up now and it's time to move on.
Thank you, goodbye.

(NOTE: If you are a user of the GLFW apprt, then please fork the project
prior to this commit or start a new project based on it. We've warned
against using it for a very, very long time now.)

This commit changes a LOT of areas of the code to use decl literals
instead of redundantly referring to the type.

These changes were mostly driven by some regex searches and then manual
adjustment on a case-by-case basis.

I almost certainly missed quite a few places where decl literals could
be used, but this is a good first step in converting things, and other
instances can be addressed when they're discovered.

I tested GLFW+Metal and building the framework on macOS and tested a GTK
build on Linux, so I'm 99% sure I didn't introduce any syntax errors or
other problems with this. (fingers crossed)

https://ziglang.org/download/0.14.0/release-notes.html#Calling-Convention-Enhancements-and-setAlignStack-Replaced

Closes #6702

This removes our mach-glfw dependency and replaces it with an in-tree
pkg/glfw that includes both the source for compiling glfw as well as the
Zig bindings. This matches the pattern from our other packages.

This is based on the upstream mach-glfw work and therefore includes the
original license and copyright information.

The reasoning is stated in the issue but to summarize for the commit:

  - mach-glfw is no longer maintained, so we have to take ownership
  - mach-glfw depended on some large blobs of header files to enable
    cross-compilation but this isn't something we actually care about,
    so we can (and do) drop the blobs
  - mach-glfw blobs were hosted on mach hosts. given mach-glfw is
    unmaintained, we can't rely on this hosting
  - mach-glfw relied on a "glfw" package which was owned by another
    person to be Zig 0.14 compatible, but we no longer need to rely on
    this
  - mach-glfw builds were outdated based on latest Zig practices