[clang-format] [feature-request] Add option to autoreplace class -> struct

In my company, coding style completely forbids the use of the `class` keyword.
Unfortunately, there is currently no option in clang-format to automatically enforce or transform this rule.

It would be very useful to add an option to clang-format to automatically replace `class` with `struct`

expected behavior:

```cpp
enum class abc ===> enum struct abc

template ===> template

template class A>
void foo();

===>

template typename A>
void foo();

class A ===> struct A

class A : a, b, c ===> struct A : private a, private b, private c
```

Start by examining clang-format and how it handles the class, enum class, and template forms shown in the issue. Define the option's expected behavior from the examples, including access defaults for transformed base classes, and add coverage demonstrating each requested transformation.

Written by the indexing model from the issue text.