Move Metamask to it's own package

[rob1997]

Summary
Currently Metamask is in the core package

Suggested features or ways to address the summary
Move package into io.chainsafe.web3-unity.metamask

Motivation
Uniformity, maintainability and lighter core package

Acceptance Criteria
Metamask is it's own package with io.chainsafe.web3-unity as a dependency

Blockers
(OPTIONAL) [Do you see any blocker that needs to be done before implementing this feature?]

Dependencies
(OPTIONAL) [Do you know about dependencies that directly affect this issue?]

Additional Context
(OPTIONAL) [Add any other context, files, images (screenshots/videos), diagrams, or documents about the feature request here.]

Final Steps

• Give it one of these labels Type: Feature Type: Enhancement
• Add your estimation

Estimations

Story Point	Amount of effort	Amount of time	Task Complexity	Task Risk or Uncerntainty
3	Mild efort	A day	Low complexity	Low

[kantagara]

Closing the issue since if we remove the mm from the default package, people wouldn't be able to use our SDK at all on webGL for sending transactions.