Move filter_executable_program_accounts to bank.rs

[pgarg66]

Problem

Accounts::filter_executable_program_accounts() makes accounts API complicated. Implementing it via trait/interface for standalone SVM will make it unnecessarily complicated.

Summary of Changes

Move filter_executable_program_accounts closer to the call site, so it can be moved into standalone SVM package.

Fixes #

[codecov]

Codecov Report

Merging #34004 (dbbc71f) into master (28e08ac) will decrease coverage by 0.1%.
The diff coverage is 100.0%.

@@            Coverage Diff            @@
##           master   #34004     +/-   ##
=========================================
- Coverage    81.9%    81.9%   -0.1%     
=========================================
  Files         811      811             
  Lines      219427   219412     -15     
=========================================
- Hits       179769   179709     -60     
- Misses      39658    39703     +45     

[LucasSte]

As in load_accounts, the only member of self we need for this function is Arc<AccountsDb>.

I was thinking of maintaining the accounts related functions as standalone and receive the Arc<AccountsDb> as a parameter. Do you think this is also valid for this case?

[pgarg66]

For the final SVM implementation we'll need a trait here instead of a specific class/object. It might be worth keeping the change simple for now. Let's see what trait definition will look like and adjust accordingly.