feat/606-enable-nat-traversal-via-hole-punching (#668)

* feat: base implementation of dcutr for hole-punching

* chore: removed circuit-relay imports from __init__

* feat: implemented dcutr protocol

* added test suite with mock setup

* Fix pre-commit hook issues in DCUtR implementation

* usages of CONNECT_TYPE and SYNC_TYPE have been replaced with HolePunch.Type.CONNECT and HolePunch.Type.SYNC

* added unit tests for dcutr and nat module and

* added multiaddr.get_peer_id() with proper DNS address handling and fixed method signature inconsistencies

* added assertions to verify DCUtR hole punch result in integration test

---------

Co-authored-by: Manu Sheel Gupta <manusheel.edu@gmail.com>

libp2p/relay/circuit_v2/pb/dcutr_pb2.pyi

@@ -0,0 +1,54 @@
+"""
+@generated by mypy-protobuf.  Do not edit manually!
+isort:skip_file
+"""
+
+import builtins
+import collections.abc
+import google.protobuf.descriptor
+import google.protobuf.internal.containers
+import google.protobuf.message
+import typing
+
+DESCRIPTOR: google.protobuf.descriptor.FileDescriptor
+
+@typing.final
+class HolePunch(google.protobuf.message.Message):
+    """HolePunch message for the DCUtR protocol."""
+    
+    DESCRIPTOR: google.protobuf.descriptor.Descriptor
+    
+    class Type(builtins.int):
+        """Message types for HolePunch"""
+        @builtins.classmethod
+        def Name(cls, number: builtins.int) -> builtins.str: ...
+        @builtins.classmethod
+        def Value(cls, name: builtins.str) -> 'HolePunch.Type': ...
+        @builtins.classmethod
+        def keys(cls) -> typing.List[builtins.str]: ...
+        @builtins.classmethod
+        def values(cls) -> typing.List['HolePunch.Type']: ...
+        @builtins.classmethod
+        def items(cls) -> typing.List[typing.Tuple[builtins.str, 'HolePunch.Type']]: ...
+    
+    CONNECT: HolePunch.Type  # 100
+    SYNC: HolePunch.Type  # 300
+    
+    TYPE_FIELD_NUMBER: builtins.int
+    OBSADDRS_FIELD_NUMBER: builtins.int
+    type: HolePunch.Type
+    
+    @property
+    def ObsAddrs(self) -> google.protobuf.internal.containers.RepeatedScalarFieldContainer[builtins.bytes]: ...
+    
+    def __init__(
+        self,
+        *,
+        type: HolePunch.Type = ...,
+        ObsAddrs: collections.abc.Iterable[builtins.bytes] = ...,
+    ) -> None: ...
+    
+    def HasField(self, field_name: typing.Literal["type", b"type"]) -> builtins.bool: ...
+    def ClearField(self, field_name: typing.Literal["ObsAddrs", b"ObsAddrs", "type", b"type"]) -> None: ...
+
+global___HolePunch = HolePunch