Optimize fs::copy

[phip1611]

Currently, FileSystem::copy

uefi-rs/uefi/src/fs/file_system/fs.rs

Lines 36 to 45 in 1b96994

	/// Copies the contents of one file to another. Creates the destination file
	/// if it doesn't exist and overwrites any content, if it exists.
	pub fn copy(
	&mut self,
	src_path: impl AsRef<Path>,
	dest_path: impl AsRef<Path>,
	) -> FileSystemResult<()> {
	let read = self.read(src_path)?;
	self.write(dest_path, read)
	}

is inefficient. It should be refactored to use a 2 MiB buffer or so to avoid allocations of possibly multiple gigabytes.

[medhefgo]

Not to mention dumb firmware shitting itself with large buffers. I'd recommend 1MiB buffers like the kernel does.