fix(filesystem): handle case-insensitive renames on all OSs

[iusx]

error

helloworld.c and Helloworld.c are recognized as the same file

I found a small issue with neo-tree. For example, if your file is named:

helloworld.c

and you want to rename it to:

Helloworld.c

you will get the warning: already exists, canceling.

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Neovim version information:

NVIM v0.10.4
Build type: Release
LuaJIT 2.1.1741730670
Run ":verbose version" for more info

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System info:

Darwin IUSX 24.1.0 Darwin Kernel Version 24.1.0: Thu Oct 10 21:03:11 PDT 2024; root:xnu-11215.41.3~2/RELEASE_ARM64_T6020 arm64

I know this issue doesn’t exist on Linux, but it does exist on my macOS system. This PR might have some issues, but it works fine on my system and fixes the problem. However, the code might not be very elegant.

[iusx]

OMG, I had no idea that was possible! You’re awesome—thanks a ton, I learned so much