[examples] Adding `core_high_dpi` example

This example enables HIGHDPI and renders a scale showing how the logical
size compares to the pixel size of the window.

Update rcore_desktop_sdl.c

Prevent immediate window restore from minimize in core_window_flags

Uncomment SetTargetFPS in core_window_flags

Improve description of RestoreWindow

Restore window currently says it sets the window state to:

   "not minimized/maximized"

However, if a window is maximized and then minimized, it's typical that
it would restore back to being maximized, which is what seems to happen
from my testing. I've reworded the description to better reflect
this behavior.

[build] only include rglfw.c for glfw platform

It looks like raylib doesn't require rglfw.c if you're using the RGFW
backend.  I'm guessing the same is true for SDL but I haven't tested.
Excluding this one file brings the raylib library down from 6.9 MB to
6.3 MB for RGFW.

However, one of the examples requires the symbols from rglfw.c,
to accomodate this I added a function that will check whether raylib has
already included rglfw and if not include it for that one example.

The core_window_flags example automatically restores the window from
being minimized after 3 seconds. However, it only resets the frameCounter
if the window is minimized through the app from inputting KEY_N.  This
means if you miminize the window by other means (like pressing the minimize
button) then the example will immediately restore the window because the
frame counter wasn't reset. I've fixed this by setting the frameCounter
back to 0 once it's expired. I also added a note in the UI that the example
automatically restores the window so it's not a surprise.

I think this line was accidently commented out in this commit:

3d1ae3500c

The FPS limit is needed to get the desired wait time for the "hide window"
test, which uses the frame counter to hide the window for 3 seconds. On
my machine without this limit it runs at over 1000 FPS and it appears
like the hide window state is broken.

I also added some text that tells the user that it only hides the window
for 3 seconds so they're not surprised when the window automatically
reappears.

Avoid divide by 0 in core_custom_frame_control example

raylib app crashing when started and a gamepad is already connected to the PC (even if the gamepad is not used in the app). I only tested this with a gamepad that has a layout which is not recognized. Using SDL3 as backend.

[build] remove examples/build.zig, incorporate into main build.zig

Removes the second build.zig in the examples directory and incorporates it
into the main build.zig. This gives the zig build system the data needed to
know if the raylib library needs to be rebuilt when running any example.

[rcore] fix: TRACELOG upon successfully changing directory

InitWindow() prints CWD during initialization,
but ChangeDirectory() does not, which is quite confusing when you start
messing with CWD. Now said function should log similar message.

I'm sorry... I did not detect this change was breaking batching... :(

[examples] use logarithmic zoom scaling in 2d camera examples

This compensate for slower zoom speed due to log scaling

The support for the scissor test has been implemented for clearing as well as for triangle clipping.
The implementation for lines and points is still missing.

I also removed the 2D clipping of lines that used the Cohen-Sutherland algorithm, opting instead to always use the Liang-Barsky algorithm in all cases.
This simplifies the implementation, and the 2D version would have caused issues when interpolating vertices in the future if we want to implement additional features.