Renames fns to get_account_shared_data()

[brooksprumo]

Problem

Since #774, we now have get_account(), get_stored_account(), get_stored_account_meta(), and get_account_shared_data() methods, but AppendVec::get_stored_account() returns an AccountSharedData. I find this a bit confusing. If we rename get_stored_account(), I think that would help.

Summary of Changes

Renames the methods to get_account_shared_data() and updates callers.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.9%. Comparing base (8c5a33a) to head (93cc7f2).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #782   +/-   ##
=======================================
  Coverage    81.9%    81.9%           
=======================================
  Files         851      851           
  Lines      231480   231480           
=======================================
+ Hits       189745   189774   +29     
+ Misses      41735    41706   -29     

[jeffwashington]

lgtm

[brooksprumo]

Had to resolve merge conflicts due to #783, so I've rebased and force-pushed. No changes to the code though.

[jeffwashington]

lgtm