native VP pre/post with storage_api::StorageRead trait lifetime issue

[tzemanovic]

trying to use a function such as

pub fn with_storage<S>(storage: &S) -> storage_api::Result<Something> {
  storage.read(some_key)
}

with native VP context .pre()/.post() currently fails with e.g. with_storage(&ctx.pre()):

error: implementation of `namada_core::ledger::storage_api::StorageRead` is not general enough
   = note: `ledger::native_vp::CtxPreStorageRead<'_, 'a, DB, H, CA>` must implement `namada_core::ledger::storage_api::StorageRead<'0>`, for any lifetime `'0`...
   = note: ...but `namada_core::ledger::storage_api::StorageRead<'_>` is actually implemented for the type `ledger::native_vp::CtxPreStorageRead<'_, '_, DB, H, CA>`

This looks like it's related to rust-lang/rust#70263, but hopefully rewriting StorageRead with GATs to avoid the explicit lifetime should get us around it.

[tzemanovic]

wait for #736