Inline comments on enums values are moved

[hzeller]

A very common way to document enums is to add EOL comments to the constants:

bazel-bin/xls/dslx/dslx_fmt - <<EOF
enum Foo : u8 {
  X = u8:1,  // Description of X
  Y = u8:2,  // Description of Y
  Z = u8:3,  // Description of Z
}
EOF

... after formatting, the outcome is less helpful:

enum Foo : u8 {
    X = u8:1,
    // Description of X
    Y = u8:2,
    // Description of Y
    Z = u8:3,
    // Description of Z
}

[cdleary]

It should have been putting them /before/ the item, but also we have support for inline comments on struct field members, need to factor out the handling so it's common to all "member items" definitions.