fix: Fix optional accounts in `declare_program!`

[cryptopapi997]

When using optional accounts with declare_program! the generated code results in the account being set to crate::ID when the account is None. This means we get two scenarios:

• If our program A is called from another program B via CPI, it will set the optional account to B if it's none because from that scope the current crate::ID is that of the calling program.
• If our program A is used from someplace that isn't another program, the macro blows up because crate::ID isn't defined anywhere.

Both of these are the wrong thing to happen, but the fix is easy - just pass in super::__ID instead, which is what this PR does.

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[cryptopapi997]

wdyt @acheroncrypto

[cryptopapi997]

Thanks for merging! Do you already have an ETA for the next patch release that will include these?

[acheroncrypto]

ETA is early next month, but you can already use it from git if you don't publish crates:

[dependencies]
anchor-lang = { git = "https://github.com/coral-xyz/anchor", rev = "b76d1bf" }

and in Anchor.toml:

anchor_version = "0.30.0-b76d1bf"