lnaddr: rename LnAddr -> bolt11

The LnAddr, lndecode and lnencode naming didn't imply that it is
bolt 11 specific, making it confusing to work with, now that there are
also bolt 12 "lnaddr".
Renaming it to *bolt11* creates a clear separation to bolt 12 things and
reduces mental load.

This commit is pure renaming (using the PyCharm IDE refactor function),
except for the removal of the `object` inheritance of LnAddr/BOLT11Addr,
this is Python 2 legacy.

electrum/lnurl.py

@@ -12,7 +12,7 @@ import aiohttp.client_exceptions
 
 from electrum import segwit_addr, util
 from electrum.segwit_addr import bech32_decode, Encoding, convertbits, bech32_encode
-from electrum.lnaddr import LnDecodeException, LnEncodeException
+from electrum.bolt11 import BOLT11DecodeException, BOLT11EncodeException
 from electrum.network import Network
 from electrum.logging import get_logger
 from electrum.i18n import _
@@ -47,11 +47,11 @@ def decode_lnurl(lnurl: str) -> str:
     hrp = decoded_bech32.hrp
     data = decoded_bech32.data
     if decoded_bech32.encoding is None:
-        raise LnDecodeException("Bad bech32 checksum")
+        raise BOLT11DecodeException("Bad bech32 checksum")
     if decoded_bech32.encoding != Encoding.BECH32:
-        raise LnDecodeException("Bad bech32 encoding: must be using vanilla BECH32")
+        raise BOLT11DecodeException("Bad bech32 encoding: must be using vanilla BECH32")
     if not hrp.startswith("lnurl"):
-        raise LnDecodeException("Does not start with lnurl")
+        raise BOLT11DecodeException("Does not start with lnurl")
     data = convertbits(data, 5, 8, False)
     url = bytes(data).decode("utf-8")
     return url
@@ -62,7 +62,7 @@ def encode_lnurl(url: str) -> str:
     try:
         url = url.encode("utf-8")
     except UnicodeError as e:
-        raise LnEncodeException("invalid url") from e
+        raise BOLT11EncodeException("invalid url") from e
     bech32_data = convertbits(url, 8, 5, True)
     assert bech32_data
     lnurl = bech32_encode(