Simplify "can call X method" use case

[quasilyte]

Implements() would miss a few cases that can be solved by a custom filter, but for the simplest cases like below we should be able to use a simple builtin.

func writeByte(m dsl.Matcher) {
	// utf8.RuneSelf:
	// characters below RuneSelf are represented as themselves in a single byte.
	const runeSelf = 0x80
	m.Match(`$w.WriteRune($c)`).
		Where(m["w"].Type.Implements("io.ByteWriter") && (m["c"].Const && m["c"].Value.Int() < runeSelf)).
		Suggest(`$w.WriteByte($c)`)
}

Unfortunately, this will not work for values that have a type of T, but implement interface only by pointer (so, only *T values will match here). For this particular case, this code will be checked without warnings (bad):

var buf bytes.Buffer
buf.WriteRune('\n')

What we want to check here is that $w.WriteRune can be rewritten as $w.WriteByte.

Maybe this API can be OK:

Where(m["w"].Type.HasMethod("WriteByte(byte) error"))

For simplicity, we can allow 1-method interfaces as arguments too:

Where(m["w"].Type.HasMethod(`io.ByteWriter`))

This new method should be at least as fast as the current approach (or even faster).