Runtime: Module to Migrate Built-In Programs to BPF

[buffalojoec]

I'm introducing this PR as a draft to hopefully gather some feedback on the
approach and some of the various things this migration path touches.

I've carefully structured the commits to ensure maximum readability, including
saving the Bank modifications required for testing the migrations for last.

---

Problem

Now that SIMD 0088
has been merged, the runtime requires a code path for migrating built-in
programs to Core BPF.

Solution

The static BUILTINS list, which houses the source-of-truth for all runtime
built-in programs, contains a feature_id field for activating new built-in
programs.

Building on this architecture, I've included a new field for
core_bpf_migration configurations, which the runtime can use on epoch rollover
to migrate a built-in to Core BPF and ensure it's handled properly by both the
Bank and the program cache.

The config defines two main fields:

• Source BPF Program: The upgradeable BPF program that will be moved in place of
  the built-in.
• Feature ID: The feature ID whose activation will trigger the migration.

To ensure maximum safety when enabling migrations, I've abstracted all of the
checks and account manipulation required to perform the migration away into the
builtin module's sub-module core_bpf_migration.

To migrate a built-in program to Core BPF, contributors need only add the source
program ID and the feature ID to the built-in's config.