Build all target architectures using github actions

[drcjt]

Current GitHub actions is only building one target architecture - TRS80 - but really need multiple builds/test runs for each target architecture.

Target architectures include:

• TRS-80
• ZX Spectrum
• CPM

[drcjt]

Need to alter build workflows to:

• [x] Build, Test, Analyse for primary target platform
• [x] Build Samples for each target platform

No point in running tests across platforms as tests do not cover any platform specific behaviour

[drcjt]

Main build is now building for trs80 and zxspectrum platforms and artifacts for the samples are being published.

Need to add cpm though