Evidence event is missing the arbitrable address which is tied to the `externalDisputeID`

[jaybuidl]

Problem

The externalDisputeID is local to a particular arbitrable and is emitted by the Arbitrable.DisputeRequest event.

Later when a court user calls submitEvidence() they reference this externalDisputeID as part of Evidence event, but it does not specify the arbitrable relevant to this externalDisputeID.

⚠️ Edge case: if the arbitrable calls EvidenceModule.submitEvidence() then this adjacent issue is relevant #2160

Solution

Add an _arbitrable parameter to IEvidence.submitEvidence() and the Evidence event.

Security Considerations

A malicious user may spoof the value of _arbitrable when submitting evidence. As long as this information is used only for the purpose of displaying evidence, it falls into 3 cases:

1. _arbitrable is the correct value, no problem.
2. _arbitrable is another arbitrable where the _externalDisputeID exists, then the evidence is displayed for that other incorrect dispute.
   -> If an attacker wants to achieve this, they can already do it today, so it does not increase the attack surface.
3. _arbitrable is something else, then _externalDisputeID won't match anything and the evidence won't be displayed.

[jaybuidl]

Following #2168 we do not need externalDisputeID at anymore so this issue can be cancelled.