Add AsRef<AccountInfo> for AccountInfo

[fanatid]

Ref solana-foundation/anchor#608

Problem

In project-serum/anchor we want to optimize code generation with something like:

pub trait KeyRef<'info> {
    fn key(&self) -> &'info Pubkey;
}

impl<'info, T> KeyRef<'info> for T
where
    T: AsRef<AccountInfo<'info>>,
{
    fn key(&self) -> &'info Pubkey {
        self.as_ref().key
    }
}

of course this produce error:

upstream crates may add a new impl of trait `std::convert::AsRef<solana_program::account_info::AccountInfo<'_>>` for type `solana_program::account_info::AccountInfo<'_>` in future versions

Summary of Changes

Implement AsRef<AccountInfo<'a>> for AccountInfo<'a>.

[mvines]

lgtm but would you mind also adding a quick test for this, one that'll yell if somebody removes this in the future

[fanatid]

Good idea 👍 Test added.

[codecov]

Codecov Report

Merging #19235 (169da11) into master (a0e8b86) will increase coverage by 0.0%.
The diff coverage is 100.0%.

@@           Coverage Diff           @@
##           master   #19235   +/-   ##
=======================================
  Coverage    82.8%    82.8%           
=======================================
  Files         455      455           
  Lines      130032   130041    +9     
=======================================
+ Hits       107738   107763   +25     
+ Misses      22294    22278   -16     

[mvines]

Thanks! This'll ship in Solana v1.7.11