Fix Issue 20315 - checkaction=context fails for const(void[]) argument

[MoonlightSentinel]

The old implementation checked only for mutable void[].
The diff is slightly larger because i joined the (void[]), (some string) and (some other slice) branches to avoid redundant type checks.

The second commit enables actual formatting for void[] as an array of bytes instead of omitting it.

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	20315	normal	checkaction=context fails for const(void[]) argument

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub fetch digger
dub run digger -- build "master + druntime#2837"