Runtime: Core BPF Migration: Struct for loading and checking source BPF program accounts

[buffalojoec]

This is chunk 4/7 of the broken-up PR #79.

Problem

When the runtime desires to migrate a builtin program to Core BPF, it will do
so by replacing the builtin program's program account with that of a BPF
upgradeable program's program account, which will contain a pointer to its
corresponding program-data account.

Currently, there exists no reliable method in the bank or runtime more broadly
for loading a BPF upgradeable program's accounts and performing various
checks to ensure both program and program-data account are configured as
expected.

Being able to run these checks before fetching the program's accounts is
extremely important for ensuring a smooth migration to Core BPF.

Summary of Changes

Within the builtins submodule, add a module specifically for core_bpf_migration,
and inside of it create a new structure for loading a source BPF upgradeable program's
program and program-data account and running checks.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 89.94083% with 17 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.8%. Comparing base (c867522) to head (6aea930).
⚠️ Report is 7002 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##           master     #332     +/-   ##
=========================================
- Coverage    81.9%    81.8%   -0.1%     
=========================================
  Files         840      841      +1     
  Lines      228098   228245    +147     
=========================================
+ Hits       186818   186929    +111     
- Misses      41280    41316     +36     

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[buffalojoec]

Note this can go in separate from #318.

[CriesofCarrots]

Despite the number of comments, this seems pretty close. Nothing major 😅