fix: Handle named ancestors in Tesla.Mock

[howleysv]

The process $ancestor list can contain named processed as well as pids in certain supervision tree structures. This PR fixes a crash that happens with Tesla.Mock when a mocked module is called from within a spawned task within a named supervision tree, by looking up the pid of the named process if it exists.

Here is a trivial example showing the problematic $ancestors behaviour that causes the error

iex(1)> Supervisor.start_link([{Task.Supervisor, name: MyTaskSup}], [name: MySup, strategy: :one_for_one])
{:ok, #PID<0.109.0>}
iex(2)> Task.Supervisor.async(MyTaskSup, fn -> :erlang.get(:"$ancestors") end) |> Task.await()
[#PID<0.110.0>, MySup, #PID<0.108.0>, #PID<0.98.0>]

[yordis]

🚀 💜