Add SKALE Europa to Assets Controller

[TheGreatAxios]

Explanation

• What is the current state of things and why does it need to change?

• This adds support for the SKALE Europa Mainnet. This works in parallel with 25578

• What is the solution your changes offer and how does it work? No core changes were made, just additional support for a new default network.
• Are there any changes whose purpose might not obvious to those unfamiliar with the domain? N/A
• If your primary goal was to update one package but you found you had to update another one along the way, why did you do so? N/A
• If you had to upgrade a dependency, why did you do so? N/A

References

Associated with 25578

Changelog

@metamask/assets-controller

• <ADDED>: Add SKALE Network Europa Hub as a default network
• <ADDED>: Add skale_europa_mainnet to enum SupportedTokenDetectionNetworks in ./src/assetsUtil.ts
• <ADDED>: Add a test case for adding the new network to assetsUtil.test.ts
• <ADDED>: Add SKALE Europa Single call balance contract to record in ./src/AssetsContractController.ts

Checklist

• [x] I've updated the test suite for new or updated code as appropriate
• [x] I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• [x] I've highlighted breaking changes using the "BREAKING" category above as appropriate