Fix incorrect build architectures in GitHub Actions

[doblon8]

This PR fixes the problems with CI builds for macOS x86_64 and Linux arm64 binaries, as reported in issue #97.

Previously, some jobs were using runner images that did not match the intended target architecture:

• macOS x86_64 was built on an arm64 runner.
• Linux arm64 was built on an x86_64 runner.

As a result, the macOS x86_64 and Linux arm64 binaries were built with the wrong architecture.

This change assigns the correct runner image to each job so that builds match their intended targets.

Additionally, the matrix strategy has been removed since each job only used a single configuration, and os / arch are now defined via env to keep the existing steps unchanged.

[doblon8]

As shown below, the architectures now match the expected targets:

user@host:/tmp/openpnp-capture$ file libopenpnp-capture-macos-latest-arm64.dylib 
libopenpnp-capture-macos-latest-arm64.dylib: Mach-O 64-bit arm64 dynamically linked shared library, flags:<NOUNDEFS|DYLDLINK|TWOLEVEL|WEAK_DEFINES|BINDS_TO_WEAK|NO_REEXPORTED_DYLIBS>

user@host:/tmp/openpnp-capture$ file libopenpnp-capture-ubuntu-22.04-arm64.so 
libopenpnp-capture-ubuntu-22.04-arm64.so: ELF 64-bit LSB shared object, ARM aarch64, version 1 (SYSV), dynamically linked, BuildID[sha1]=98c36ccda46bbdce3d341ad54be1e16e6f0a0673, not stripped

user@host:/tmp/openpnp-capture$ file libopenpnp-capture-ubuntu-22.04-x86_64.so 
libopenpnp-capture-ubuntu-22.04-x86_64.so: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, BuildID[sha1]=55e814b800e8712b04fdf005c03ecc8194502acf, not stripped

user@host:/tmp/openpnp-capture$ file libopenpnp-capture-windows-latest-x86_64.dll 
libopenpnp-capture-windows-latest-x86_64.dll: PE32+ executable for MS Windows 6.00 (DLL), x86-64, 7 sections

Note: I couldn’t verify the macOS x86_64 artifact, because I'm using a free GitHub account that doesn't allow me to run large images.