scaladoc generate invalid api doc if class name contains `/` or `\`

[xuwei-k]

Compiler version

• 3.1.2-RC1-bin-20211022-f7abd32-NIGHTLY
• 3.1.0

Minimized code

A.scala

package foo

class A

trait \/

trait /\

Output

$ tree target/scala-3.1.2-RC1-bin-20211022-f7abd32-NIGHTLY/api/foo
target/scala-3.1.2-RC1-bin-20211022-f7abd32-NIGHTLY/api/foo
├── A.html
├── \\
└── \\.html

scala3doc-bug.mov

Expectation