This change replaces individual private members in tcp.endpoint with a single
private TCPEndpointState member.
Some internal substructures within endpoint (receiver, sender) have been broken
into a public substructure (which is then copied into the TCPEndpointState
returned from completeState()) alongside other private fields.
Fixes#4466
PiperOrigin-RevId: 369329514
Based on the guidelines at
https://opensource.google.com/docs/releasing/authors/.
1. $ rg -l "Google LLC" | xargs sed -i 's/Google LLC.*/The gVisor Authors./'
2. Manual fixup of "Google Inc" references.
3. Add AUTHORS file. Authors may request to be added to this file.
4. Point netstack AUTHORS to gVisor AUTHORS. Drop CONTRIBUTORS.
Fixes#209
PiperOrigin-RevId: 245823212
Change-Id: I64530b24ad021a7d683137459cafc510f5ee1de9
