feat/bin-e2e: Generalize fibonacci example to e2e bin

[naure]

• Upgrade example code to a CLI.
• Load ELF from file.
• Works with multiple programs including:
  • sp1 fibonacci.elf
  • ceno examples/*

Example commands:

cargo run --package ceno_zkvm --bin e2e -- --max-steps=100 --platform=sp1 ceno_zkvm/examples/fibonacci.elf

cargo run --package ceno_zkvm --bin e2e -- examples/target/riscv32im-unknown-none-elf/release/examples/ceno_rt_mini

Not included:

heap, IO, or generally memory not allocated in ELF headers.