Calling `dict()` on `av.dictionary.Dictionary` object cause `ValueError`

[laggykiller]

Occurs in main branch, not in previously released versions.

from av.dictionary import Dictionary
options = Dictionary({"quality": "95"})
dict(options)

Would cause ValueError: dictionary update sequence element #0 has length 7; 2 is required

Practically, this would cause error here:

PyAV/av/codec/context.py

Line 253 in 99087dd

self.options = dict(options)

[laggykiller]

According to https://github.com/python/typeshed/blob/main/stdlib/builtins.pyi, python builtin dict() has multiple __init__() methods, notably the following:

class dict(MutableMapping[_KT, _VT]):
    @overload
    def __init__(self, map: SupportsKeysAndGetItem[_KT, _VT], /) -> None: ...
    @overload
    def __init__(self, iterable: Iterable[tuple[_KT, _VT]], /) -> None: ...

and SupportsKeysAndGetItem is defined as:

class SupportsKeysAndGetItem(Protocol[_KT, _VT_co]):
    def keys(self) -> Iterable[_KT]: ...
    def __getitem__(self, key: _KT, /) -> _VT_co: ...

Since av.dictionary.Dictionary does not have keys() method, it is treated as Iterable instead of SupportsKeysAndGetItem, and python tries to create dict by iterating av.dictionary.Dictionary (__iter__() yields key only, not key-value pair)

I propose #2179 which implements keys() method and hence solve the problem