feat: add session key executor

[moldy530]

Pull Request Checklist

• Did you add new tests and confirm existing tests pass? (yarn test)
• Did you update relevant docs? (docs are found in the site folder, and guidelines for updating/adding docs can be found in the contribution guide)
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• Does your PR title also follow the Conventional Commits standard?
• If you have a breaking change, is it correctly reflected in your commit message? (e.g. feat!: breaking change)
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PR-Codex overview

Focus of the PR:

This PR focuses on adding a SessionKeyExecutor to the accounts package.

Detailed summary:

• Added SessionKeyExecutor to index.ts in the accounts package.
• Imported necessary types from @alchemy/aa-core and viem.
• Exported SessionKeyExecutor as an Executor function.
• Implemented encodeExecute and encodeBatchExecute functions in SessionKeyExecutor.
• Used encodeFunctionData to encode function data with the SessionKeyPluginAbi.
• Handled the case when the account is not connected to an owner.

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