svm: speed up filter_executable_program_accounts

[2501babe]

Problem

presently, filter_executable_program_accounts makes an expensive accounts-db lookup for every account in every transaction batch. this used to be an unfortunate necessity because account loading could not happen until the local program cache was built. a recent feature gate activation has severed that dependency, giving us freedom to improve this

Summary of Changes

create a local program cache for every transaction, instead of every batch, and do this after the transaction accounts have been loaded. this allows us to obviate all accounts-db lookups in filter_executable_program_accounts for checking if an account is owned by a program loader because we already have that information. based on testing done by @alessandrod, this speeds up transaction execution by 30-40%

this pr will be immediately followed by another which removes nearly all accounts-db lookups from replenish_program_cache as well. this pr will remain a draft until then; they are spiritually similar but split into two for readability and ease of review

edit: this pr will not be as easy as originally hoped. there are some challenges moving from a per-batch to a per-tx cache (our ultimate goal) due to how the current implementation handles tombstones, and some challenges using the results of account loading to incrementally update a per-batch cache (a plausible short-term goal until the local program cache can be partially redesigned to behave better)

edit2: its viable again. because the other approach is nonviable. lol. clean up the comment history later but rn im based on #4656 for test coverage and need to:

• figure out something for load_program_with_pubkey that plays nice w bank
• check modification slot somehwere when replenishing to set up tombstones. v3 this is easy. v1/v2 im not sure the right behavior... actually mb it doesnt matter? we dont really care if it goes in the cache or not if it always fails since it doesnt affect loading anymore? we only need to handle v1/2 i think

[2501babe]

this approach is non-viable without major changes to the program cache, which i want to do, but will need to loop in several people and possibly feature-gate. for now i have a relatively simple way to fix filter_executable_program_accounts. going to do it in a separate pr because this branch may be useful in the future

[2501babe]

as noted in #4574 we will in fact need to rework the program cache because there is no safe way to do this except per-transaction, after account loading