Consider generating random salt when creating a delegation

[jeffsmale90]

Description

When no salt is specified in calls to createDelegation and createOpenDelegation, the default value 0x00 is used.

Generating a random salt would be safer as a caller creating a delegation would not expect two delegations created with the same arguments to be considered the same delegation which is the current behaviour.

Technical Details

Consider exporting a generateSalt function from @metamask/delegation-core so that core consumers don't need to reproduce this function.

Acceptance Criteria

• Are metrics required?
• Are translations required?
• Cases to satisfy
• XYZ should work
• Etc.

Scenario: xxxx

• GIVEN a user is in x state
• WHEN a user does x
• AND a user does x
• THEN x should occur

References

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• Issue numbers. Links.
• Slack threads.
• Etc.