Improve workspace handelling

[QuantumEntangledAndy]

I was having issues with this in my workspace projects so I went and fixed that

Additions

• Use cargo locate-project --workspace to find workspace manifiest
• Add cargo all which checks all workspaces and all targets
• Fix issue with paths relative to the cargo manifest root not cwd
• Adds the --all-targets option to the all varients so that it checks all binaries/examples/tests/benches

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Issues related to worskspaces Fixes #151

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Issues related to --all-targets Fixes #61 Fixes #111 (In terms of --all-targets checking all examples and tests) Fixes #113