[dev.regabi] cmd/compile/internal/types: add IsScalar query method
[dev.regabi] cmd/compile/internal/types: add IsScalar query method

Add method Type.IsScalar() method, which returns TRUE
for numeric and pointer-shaped types, false for composites
such as string/array/slice/struct.

Change-Id: Ie53c71c07c5b3fbae11b48addd172343dc6bf3fd
Reviewed-on: https://go-review.googlesource.com/c/go/+/274857
Run-TryBot: Than McIntosh <4b2922593166fc595a9b1a408f34f5d3817fe9d2@google.com>
TryBot-Result: Go Bot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Trust: Than McIntosh <4b2922593166fc595a9b1a408f34f5d3817fe9d2@google.com>
Reviewed-by: Matthew Dempsky <e56ac2c500064424afac424d4b5e53bd0570a731@google.com>

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