Handle ESP32 Arduino core 3.3.11+ mempool symbol rename for C5 builds

[Copilot]

Arduino ESP32 core 3.3.11 changed the exported NimBLE mempool symbols for controller-backed targets such as esp32c5, so NimBLE-Arduino 2.5.0 still referenced legacy r_os_* names and failed at link time. This updates the symbol selection to match the core version and adds esp32c5 to the existing Arduino build matrix to keep this path covered.

• Compatibility gate

  • In os_mempool.h, gate the legacy r_os_* aliases on Arduino core version.
  • Cores before 3.3.11 keep using ROM-backed r_os_mempool_init / r_os_memblock_get / r_os_memblock_put.
  • Cores 3.3.11+ fall back to the unprefixed os_* names exported by the newer core.

• Build coverage

  • Add esp32c5 to .github/workflows/build.yml under the Arduino ESP32 matrix so the affected target is compiled in CI.

• Documentation in code

  • Add a short comment explaining why 3.3.11 is the cutoff and keep the version-gate macro scoped to the header.

#if defined(ESP_ARDUINO_VERSION)
/* Arduino ESP32 core 3.3.11+ dropped the legacy r_ prefix for these mempool symbols. */
#define NIMBLE_OS_MEMPOOL_USE_ROM_R_PREFIX \
    (ESP_ARDUINO_VERSION < ESP_ARDUINO_VERSION_VAL(3, 3, 11))
#else
#define NIMBLE_OS_MEMPOOL_USE_ROM_R_PREFIX 1
#endif

• Fixes Regression of build 2.5.0 library with recent Core 3.3.11 for ESP32-C5 target #1174

[h2zero]

Needs to be squashed