QEMU: add injections mode default

[domenukk]

This makes injections fuzzing easier to use, and it doesn't add much overhead to the build process/downloads (especially when compared to qemu, lol)

[tokatoka]

error[E0599]: no method named `syscalls` found for reference `&hooks::QemuHooks<QT, S>` in the current scope
   --> /home/runner/work/LibAFL/LibAFL/libafl_qemu/src/injections.rs:256:15
    |
256 |         hooks.syscalls(Hook::Function(syscall_hook::<QT, S>));
    |               ^^^^^^^^ method not found in `&QemuHooks<QT, S>`

error[E0599]: no method named `mappings` found for reference `&emu::Emulator` in the current scope
   --> /home/runner/work/LibAFL/LibAFL/libafl_qemu/src/injections.rs:266:27
    |
266 |         for region in emu.mappings() {
    |                           ^^^^^^^^ method not found in `&Emulator`

error[E0599]: no method named `load_addr` found for reference `&emu::Emulator` in the current scope
   --> /home/runner/work/LibAFL/LibAFL/libafl_qemu/src/injections.rs:400:13
    |
400 |         emu.load_addr()
    |             ^^^^^^^^^ method not found in `&Emulator`

For more information about this error, try `rustc --explain E0599`.
error: could not compile `libafl_qemu` (lib) due to 3 previous errors
Error: Process completed with exit code 1.

CI fails due to injection fuzzer

[domenukk]

Will take a look