compliance: #27 - WiP compliance test plan.

 On branch dev/next-release
 Your branch is up-to-date with 'origin/dev/next-release'.

 Changes to be committed:
	modified:   README.md
	modified:   tests/compliance/README.md
	new file:   tests/compliance/test-plan-scalar.adoc

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	modified:   extern/riscv-compliance (modified content)
	modified:   extern/riscv-gnu-toolchain (modified content)
	modified:   extern/riscv-isa-sim (modified content)
	modified:   extern/sail-riscv (modified content, untracked content)