Improve pymysql.converters stubs (#6267)

I spent far too much time being confused about why pyanalyze thought `pymysql.converters.escape_dict` only takes two arguments.

I rewrote the stubs from scratch using the implementation: https://github.com/PyMySQL/PyMySQL/blob/main/pymysql/converters.py.

The "charset" argument is ignored as far as I can tell; it gets passed to other functions but no function actually uses it.

Co-authored-by: Sebastian Rittau <srittau@rittau.biz>

stubs/PyMySQL/pymysql/converters.pyi

@@ -1,47 +1,39 @@
-from typing import Any
+import datetime
+import time
+from collections.abc import Callable, Mapping, Sequence
+from decimal import Decimal
+from typing import Any, Optional, Type, TypeVar
 
-from .charset import charset_by_id as charset_by_id
-from .constants import FIELD_TYPE as FIELD_TYPE, FLAG as FLAG
+_EscaperMapping = Optional[Mapping[Type[object], Callable[..., str]]]
+_T = TypeVar("_T")
 
-PYTHON3: Any
-ESCAPE_REGEX: Any
-ESCAPE_MAP: Any
+def escape_item(val: object, charset: object, mapping: _EscaperMapping = ...) -> str: ...
+def escape_dict(val: Mapping[str, object], charset: object, mapping: _EscaperMapping = ...) -> dict[str, str]: ...
+def escape_sequence(val: Sequence[object], charset: object, mapping: _EscaperMapping = ...) -> str: ...
+def escape_set(val: set[object], charset: object, mapping: _EscaperMapping = ...) -> str: ...
+def escape_bool(value: bool, mapping: _EscaperMapping = ...) -> str: ...
+def escape_int(value: int, mapping: _EscaperMapping = ...) -> str: ...
+def escape_float(value: float, mapping: _EscaperMapping = ...) -> str: ...
+def escape_string(value: str, mapping: _EscaperMapping = ...) -> str: ...
+def escape_bytes_prefixed(value: bytes, mapping: _EscaperMapping = ...) -> str: ...
+def escape_bytes(value: bytes, mapping: _EscaperMapping = ...) -> str: ...
+def escape_str(value: str, mapping: _EscaperMapping = ...) -> str: ...
+def escape_None(value: None, mapping: _EscaperMapping = ...) -> str: ...
+def escape_timedelta(obj: datetime.timedelta, mapping: _EscaperMapping = ...) -> str: ...
+def escape_time(obj: datetime.time, mapping: _EscaperMapping = ...) -> str: ...
+def escape_datetime(obj: datetime.datetime, mapping: _EscaperMapping = ...) -> str: ...
+def escape_date(obj: datetime.date, mapping: _EscaperMapping = ...) -> str: ...
+def escape_struct_time(obj: time.struct_time, mapping: _EscaperMapping = ...) -> str: ...
+def Decimal2Literal(o: Decimal, d: object) -> str: ...
+def convert_datetime(obj: str | bytes) -> datetime.datetime | str: ...
+def convert_timedelta(obj: str | bytes) -> datetime.timedelta | str: ...
+def convert_time(obj: str | bytes) -> datetime.time | str: ...
+def convert_date(obj: str | bytes) -> datetime.date | str: ...
+def through(x: _T) -> _T: ...
 
-def escape_item(val, charset): ...
-def escape_dict(val, charset): ...
-def escape_sequence(val, charset): ...
-def escape_set(val, charset): ...
-def escape_bool(value): ...
-def escape_object(value): ...
+convert_bit = through
 
-escape_int: Any
-
-escape_long: Any
-
-def escape_float(value): ...
-def escape_string(value): ...
-def escape_unicode(value): ...
-def escape_None(value): ...
-def escape_timedelta(obj): ...
-def escape_time(obj): ...
-def escape_datetime(obj): ...
-def escape_date(obj): ...
-def escape_struct_time(obj): ...
-def convert_datetime(connection, field, obj): ...
-def convert_timedelta(connection, field, obj): ...
-def convert_time(connection, field, obj): ...
-def convert_date(connection, field, obj): ...
-def convert_mysql_timestamp(connection, field, timestamp): ...
-def convert_set(s): ...
-def convert_bit(connection, field, b): ...
-def convert_characters(connection, field, data): ...
-def convert_int(connection, field, data): ...
-def convert_long(connection, field, data): ...
-def convert_float(connection, field, data): ...
-
-encoders: Any
-decoders: Any
-conversions: Any
-
-def convert_decimal(connection, field, data): ...
-def escape_decimal(obj): ...
+encoders: dict[Type[object], Callable[..., str]]
+decoders: dict[int, Callable[[str | bytes], Any]]
+conversions: dict[Type[object] | int, Callable[..., Any]]
+Thing2Literal = escape_str