Loader-v3 programdata account size is not counted towards limit if executed through CPI

[tao-stones]

Problem

@Lichtso repots:

we are not accounting for loader-v3 programs executed through CPI here:
https://github.com/anza-xyz/agave/blob/177f722410eada6b44cd3f65d992d9a846f21106/svm/src/account_loader.rs#L280
Since it was added (in [#29743](https://github.com/solana-labs/solana/pull/29743)) it was changed once to account for loader-v3 programdata accounts, but only in top-level instructions ([#30703](https://github.com/solana-labs/solana/pull/30703)).

Only in top-level instructions we use program.account_size from the program cache which correctly includes the loader-v3 programdata account length. The else branch however does use account.data().len() which is the proxy account length.

Add a test to demonstrate it.

Proposed Solution

[jstarry]

I'd like to take on this task by refactoring the existing code and likely adding a feature gate to make this behavior consistent with other loaders.

[tao-stones]

I'd like to take on this task by refactoring the existing code and likely adding a feature gate to make this behavior consistent with other loaders.

@Lichtso do you have something in pipeline might potentially conflict with it?

[Lichtso]

Yes, but @jstarry and I already coordinated.

[jstarry]

FYI this will be addressed in @2501babe's loaded account data size SIMD here: solana-foundation/solana-improvement-documents#186