SVM: change modified programs result to hash map

[buffalojoec]

Problem

Currently, the SVM's TransactionResult requires a full local program cache
instance to return the programs modified by the transaction batch. This can
be done more elegantly with a hash map.

Furthermore, other crates who must mock out SVM transaction results can
now simply use HashMap::new(), and forego having to drag in types from
solana-program-runtime. This even removes the dependency from AccountsDB
altogether.

Summary of Changes

Change programs_modified_by_tx in the SVM's TransactionResult to be a
HashMap<Pubkey, Arc<ProgramCacheEntry>>.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.7%. Comparing base (e01278e) to head (242a8ae).
Report is 3 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1391   +/-   ##
=======================================
  Coverage    82.7%    82.7%           
=======================================
  Files         872      872           
  Lines      369436   369439    +3     
=======================================
+ Hits       305779   305803   +24     
+ Misses      63657    63636   -21     

[buffalojoec]

@Lichtso @pgarg66 This change tees up my next PR, which unifies the two local program cache instances.