Add associated token account IDL

[acheroncrypto]

Follow up on #3373, added Anchor IDL for associated-token-account program.

Please let me know if this is appropriate. I have been waiting to submit the remaining IDLs until I receive a feedback.

[joncinque]

Thanks for your contribution. Are you sure that these IDLs work? I was trying to read into how anchor generates instructions and couldn't find it in the documentation, but it looks like it might hash the instruction name in order to generate a part of the instruction data, whereas the SPL instruction data is just one byte counting up from 0.

[acheroncrypto]

Yes you are correct, Anchor programs have 8 byte discriminator up front, that's why we also use a coder. I've made a repository of SPL Anchor clients and tests here: https://github.com/acheroncrypto/native-to-anchor

Here are the tests for associated-token-address https://github.com/acheroncrypto/native-to-anchor/blob/master/client/tests/src/spl/associated-token-account.ts

I wasn't sure where to put all of these so made a repo for it, most of the SPL is tested. Curious to know what you think!

[joncinque]

Would this IDL be usable without the custom coder, which is provided in a separate library? If it requires an additional outside library, it would probably do better to live in that other library

[acheroncrypto]

Yes I agree, I think there was a miscommunication for where to submit these IDLs but now that they have been merged into Anchor coral-xyz/anchor#2143 this PR can be closed.