Simplify mutable globals with single write in "start"

It looks like simplify global pass doesn't take into account v128 types.
For example:

(module
 (global $g (mut v128) (v128.const i32x4 0x00000000 0x00000000 0x00000000 0x00000000))
 (start $~start)
 (func (export "getG") $getG (result v128)
  (global.get $g)
 )
 (func $~start
  (global.set $g
   (v128.const i32x4 0x00000003 0x00000003 0x00000003 0x00000003)
  )
 )
)

Cannot be optimized to:

(module
 (global $g (mut v128) (v128.const i32x4 0x00000003 0x00000003 0x00000003 0x00000003))
 (func (export "getG") $getG (result v128)
  (global.get $g)
 )
)

Start with the simplify global pass and reproduce the issue using the WebAssembly module in the report. Check how mutable v128 globals with a single write in the start function are handled; done when the pass safely produces the shown optimized module while preserving getG behavior.