Install Zig from tarball not from snap for CI tests

[disconnect3d]

We install Zig compiler in order to compile test binaries properly. For that, I added installation of Zig through snap packages to our test setup script:

pwndbg/setup-test-tools.sh

Lines 28 to 29 in d111c8d

	# We use zig to compile some test binaries as it is much easier than with gcc
	sudo snap install zig --classic --edge

However, this is not ideal - we use an edge version here which may change anytime.

We should pin a tarball version instead (download it, check its hash if its expected one and then unpack and use it).

[disconnect3d]

Done in

• tools: change zig to install from a tarball (fixes: #1088) #1089
• Fix zig not being installed when installed system-wide #1093