FVM contract encoding update

[AlexandraRoatis]

Description

1. Bug fix: closing the database where the VM type is stored and storing the information only if the contract creation was successful.
2. Added VM type to contract details and saved it to stored encoding assuming only FVM contracts exist on the network.

Subset of #866.

Type of change

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• Bug fix.
• New feature.
• Enhancement.
• Unit test.
• Breaking change (a fix or feature that causes existing functionality to not work as expected).
• Requires documentation update.

Testing

Please describe the tests you used to validate this pull request. Provide any relevant details for test configurations as well as any instructions to reproduce these results.

• existing test suite + tests to verify encoding switch

Verification

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• I have self-reviewed my own code and conformed to the style guidelines of this project.
• New and existing tests pass locally with my changes.
• I have added tests for my fix or feature.
• I have made appropriate changes to the corresponding documentation.
• My code generates no new warnings.
• Any dependent changes have been made.

[aion-kelvin]

looks pretty sane ... should we add any tests to make sure this vm type field gets saved now?

[AionJayT]

the rlp encode/decode order can be the original order plus the vmType. Then we can make sure the logic will be more neat and safe.

[aion-kelvin]

thanks for the test!