This adds an implementation of the Zcb code size extension.

Co-authored-by: Martin Berger <martinberger@users.noreply.github.com>

This script was used to do the modification:

```
from pathlib import Path
import re

RE_LINE = r"/\*={50,150}\*/\n"
RE_MIDDLE = r"/\*.*\*/\n"

NEW_TEXT = """/*=======================================================================================*/
/*  This Sail RISC-V architecture model, comprising all files and                        */
/*  directories except where otherwise noted is subject the BSD                          */
/*  two-clause license in the LICENSE file.                                              */
/*                                                                                       */
/*  SPDX-License-Identifier: BSD-2-Clause                                                */
/*=======================================================================================*/
"""

REPLACEMENT = re.compile(rf"^{RE_LINE}(?:{RE_MIDDLE}){{10,100}}{RE_LINE}")

def main():
    for file in Path("model").glob("**/*.sail"):
        text = file.read_text(encoding="utf-8")
        text = REPLACEMENT.sub(NEW_TEXT, text, 1)
        file.write_text(text, encoding="utf-8")

if __name__ == "__main__":
    main()
```

This strips trailing whitespace and fixes line endings. I had to add the
*.dump files to the exclude list to avoid excessive changes, but
ideally these would not be part of the repository since they can just be
generated by running objdump manually.