Add BPF Loader 2 to cache

[buffalojoec]

Add the BPF Loader 2 to the default program cache. This allows Mollusk
to support CPI to BPF Loader 2 programs.

cc @OliverNChalk

[buffalojoec]

Just a general note for anyone following.

Rather than add all of the builtins to the cache, like the runtime does, I'd rather not add unnecessary dependencies to Mollusk - like the lookup table program, or stake/vote. Instead, if developers need those builtins, they can add those crates to their development dependencies and add them themselves through Mollusk's program API.

All builtins besides system and BPF Loaders are thus opt-in only.