Re-organize Modules

[Reisen]

This PR re-organizes many of the modules in the current Rust rewrite of the oracle contract, in particular:

1: Creates accounts.rs for PythAccount

This moves PythAccount into its own module, and moves methods from utils that are parameterized by unconstrained T, this allows the methods to be correctly bound to their impls, all call-sites change in this way:

- initialize_pyth_account_checked::<MappingAccount>(&account_info)?
+ MappingAccount::initialize(&account_info)?

All account specific helpers from utils.rs are then moved to accounts.rs to move away from the utils.rs anti-pattern. Each individual account exists under accounts/ which also means associated data can be colocated with the account, such as the PERMISSIONS seed which now lives in accounts/permission.rs.

2: Moves handlers under processor/

This removes the rust_oracle module and moves handlers under the processor module, each handler has its own module which makes it easier to colocate functions that are only related to specific handlers. For example the c_upd_aggregate function now lives in processor/upd_price.rs

These two changes nearly empty c_oracle_header.rs which was an ad-hoc place for account definitions and utilities. The rest of utils.rs can also be refactored, but as a separate PR.

[guibescos]

Let's do it