Mock method parameter shadows unexported types

Please consider the following snippet:

```go
package main

type s struct{}

//go:generate moq -out i_test.go . i
type i interface {
m(s s)
}
```

moq generates:

```go
// m calls mFunc.
func (mock *iMock) m(s s) { // Type s is shadowed.
if mock.mFunc == nil {
panic("iMock.mFunc: method is nil but i.m was just called")
}
callInfo := struct {
S s // Compiler error: s (variable of type s) is not a type.
}{
S: s,
}
mock.lockm.Lock()
mock.calls.m = append(mock.calls.m, callInfo)
mock.lockm.Unlock()
mock.mFunc(s)
}
```

This may (and arguably should) be remedied by changing the interface method to `m(somethingDescriptive s)`, yet it's an invalid output generated from a valid input.

Reproduce the interface and go:generate command from the issue, then trace the generator entry point that emits mock method parameters and call-info structs. Add a regression case for the unexported type name and verify that the generated Go compiles without the parameter shadowing its type.

Written by the indexing model from the issue text.