Update syscalls code in definitions

[LucasSte]

Problem

SIMD-0178 introduces a new scheme for syscalls, whereby each syscall is assigned a defined integer according to a table.

Static syscalls, albeit added to the repository a while ago, don't yet follow the new code convention.

Summary of Changes

Created a file in define-syscalls to maintain all codes, updated the syscall declaration macros and the syscall registration in rBPF.

Ideally, we could create variables for the syscall names used in syscall registration on rBPF, but the concat_idents Rust macro isn't yet stabilized to allow a clean Rust code with a macro.

[mergify]

The Firedancer team maintains a line-for-line reimplementation of the
native programs, and until native programs are moved to BPF, those
implementations must exactly match their Agave counterparts.
If this PR represents a change to a native program implementation (not
tests), please include a reviewer from the Firedancer team. And please
keep refactors to a minimum.