Add cyclic pattern generation and offset calculation

[AO031]

This PR adds two utility functions to misc.py:

• cyclic(length=None): generates a de Bruijn sequence pattern of 4‑byte tokens (aaaa, aaab, ..., zzzz) for buffer overflow testing. If length is given, returns the first length bytes.
• cyclic_find(subseq): returns the byte offset of a 4‑byte token in the pattern. Accepts a 4‑character string or a little‑endian integer (e.g., from EIP). Returns -1 if the token is invalid.

These functions are commonly used in exploit development to quickly determine the exact offset to overwrite the return address. They are analogous to pwntools' cyclic and cyclic_find, but implemented natively in pure Python without external dependencies.

Usage example:

from winpwn import cyclic, cyclic_find

# Generate 200-byte pattern
pattern = cyclic(200)
# ... send pattern to target ...

# After crash, get EIP value (e.g., 0x64616161)
offset = cyclic_find(0x64616161)
print(f"Offset: {offset} bytes")   # Output: 12
OR
offset = cyclic_find("aaad")
print(f"Offset: {offset} bytes")   # Output: 12