Incorrect remove of feFunc* attr

[RichardLuo0]

This issue proposes a bug which...

Background & Context

<!DOCTYPE xml>
<svg xmlns="http://www.w3.org/2000/svg">
  <defs>
    <filter>
      <feTurbulence result="noiseImage" type="fractalNoise" baseFrequency="0.6" numOctaves="2"
        seed="0"
        stitchTiles="stitch" />
      <feComponentTransfer result="noise" in="noiseImage">
        <feFuncA type="linear" slope="0.02" />
      </feComponentTransfer>
    </filter>
  </defs>
</svg>

After sanitize, the slope is removed. Not only slope, other attr that can be used on feFunc* will be removed.

Given output

<svg xmlns="http://www.w3.org/2000/svg">
  <defs>
    <filter>
      <feTurbulence stitchTiles="stitch" seed="0" numOctaves="2" baseFrequency="0.6" type="fractalNoise" result="noiseImage"></feTurbulence>
      <feComponentTransfer in="noiseImage" result="noise">
        <feFuncA type="linear"></feFuncA>
      </feComponentTransfer>
    </filter>
  </defs>
</svg>

Expected output

The slope is preserved

<!DOCTYPE xml>
<svg xmlns="http://www.w3.org/2000/svg">
  <defs>
    <filter>
      <feTurbulence result="noiseImage" type="fractalNoise" baseFrequency="0.6" numOctaves="2"
        seed="0"
        stitchTiles="stitch" />
      <feComponentTransfer result="noise" in="noiseImage">
        <feFuncA type="linear" slope="0.02" />
      </feComponentTransfer>
    </filter>
  </defs>
</svg>