Get rid of obsolete __ArrayEq lowering

[kinke]

Checking arrays of different element types for equality is handled by the (more recent) __equals() lowering, rendering __ArrayEq obsolete and enabling to get rid of duplicated functionality in druntime, see: https://github.com/dlang/druntime/blob/9ce4a36f1f4edb73683775e5824272da9e27dccc/src/core/internal/array/equality.d#L56-L65

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[thewilsonator]

This looks good, is it still draft?

[kinke]

I thought it'd be a trivial little change, but it turned out more involved and probably need some more analysis. I might also look into the different-floating-points => creal conversion, one of the surprises of the surrounding code.

[ibuclaw]

I thought it'd be a trivial little change, but it turned out more involved and probably need some more analysis. I might also look into the different-floating-points => creal conversion, one of the surprises of the surrounding code.

It might be about time to put creal on a proper deprecation path.

[wilzbach]

It might be about time to put creal on a proper deprecation path.

... #7640

[MoonlightSentinel]

This PR apparently fixed https://issues.dlang.org/show_bug.cgi?id=21012 along the way.