Ast10x0 : FMC flash backend for the flash service

[rusty1968]

This PR depends on #365

Tests

The service is exercised end-to-end through the full IPC stack (FlashIpcClient → server → BlockingFlash → Ast10x0FmcFlashDriver → FMC CS0), not just at the peripheral level.

• flash_qemu_test — runs under emulation, no hardware required
• flash_evb_test — the same system image on real AST10x0 EVB hardware

[yvettewu1]

Tested with ast1060 evb board:

1. The flash test itself passed: the client completed geometry, erase, program, read-back, and restore, then printed flash client PASS.
2. The later HardFault was caused by the target shutdown path calling semihosting exit(), which works under QEMU/debugger-style environments but can trap as a HardFault on bare AST10x0 EVB hardware.

Tested with the following changes and no more HardFault:

-use cortex_m_semihosting::debug::{exit, EXIT_FAILURE, EXIT_SUCCESS};
+use console_backend::console_backend_write_all;

-exit(status);
+let _ = console_backend_write_all(sentinel);

[rusty1968]

Your code is explicitly dependent of the std crate. Just take a look at producer : Vec<Box> is double heap here — the Vec allocates the array and each Box allocates a provider. We do not have a memory allocator in an embedded environment. OpenPRoT is no alloc.