Add support for external accounts

[febo]

This PR adds support for loading external accounts as dependencies. These are specified on Cargo.toml as a list of addresses under a account-dependencies property – e.g.,:

[package.metadata.solana]
program-id = "11111111111111111111111111111111"
account-dependencies = ["SysvarC1ock11111111111111111111111111111111"]

[changeset-bot]

🦋 Changeset detected

Latest commit: d81e2d2

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
create-solana-program	Patch

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[lorisleiva]

Amazing, thanks for that Febo! Just a couple of small comments but it looks good to me.

[lorisleiva]

Thanks Febo! 👌