espressif: add optional ESP-Hosted Wi-Fi on ESP32-P4

[ladyada-eagleclaw]

AI-assisted with Codex, asked to bring up the Metro ESP32-P4's C6 coprocessor through CircuitPython's standard Wi-Fi APIs. This PR extracts only ESP-Hosted integration from #11497; the Metro wiring is in the separate board PR.

What

Add optional ESP-Hosted Wi-Fi to ESP32-P4 boards. CIRCUITPY_ESP_HOSTED=1 enables the existing wifi, socketpool and SSL implementation with the remote radio; each board provides its SDK transport configuration.

Pin ESP-Hosted v2.12.13 and an upstream esp-wifi-remote commit (component 1.6.5), wire them into dependency/build selection, select the remote Wi-Fi headers, initialize Hosted once, and retain the SDIO/control pins across VM reloads. Reserve the Hosted SDMMC slot so sdioio selects the other slot. Keep dependency selection consistent during automatic CMake regeneration.

Dependency

This PR is stacked on #11500 (fix-sdio-slot-lifetime), which contains the separately reviewed controller/slot cleanup and SDK prerequisites. Its diff contains only the Hosted integration. The unrelated SD frequency-unit correction, USB host, ADC, UID, ROM reset and DSI fixes are separate PRs.

Validation

Metro ESP32-P4 Rev A, silicon v0.1, 16 MB flash/PSRAM, with C6 firmware ESP-Hosted 2.12.11. AP scans, connection/DHCP, gateway ping, DNS resolution and HTTP 200 passed. After normal reboot, safe-mode reason was NONE, gateway ping was 19 ms and the HTTP response was HTTP/1.1 200 OK.

The same integrated firmware passed concurrent SD-card read/write verification and 24 mount/read/unmount/deinit cycles while Wi-Fi scanned, then returned to the USB keyboard/DSI demo. These are serial and hardware observations, not simulated results. Credentials were not added to the source or PR.

Recombining the eight issue-specific changes and the board definition reproduces all 29 affected paths from the tested integration tree byte for byte. That recombined tree builds on current main (35210c2e31) with make -C ports/espressif BOARD=adafruit_metro_esp32p4 BUILD=build-metro-p4-c6-final -j6: 1,536,144 bytes used and 561,008 bytes free in the 2 MiB firmware partition. Earlier integrated builds also passed for the other five P4 configurations and an ESP32-S3. This is a combined build with the separately submitted Metro wiring, not a claim of a standalone hardware test of the extracted PR. Changed-file pre-commit and git diff --check pass. The C6 firmware was not modified. BLE, ESP-NOW, TLS validation and other coprocessor/transport combinations are not claimed.

[mikeysklar]

Metro CI fails with "No SOURCES given to target: __idf_esp-hosted". CI never fetches esp-hosted's nested protobuf-c submodule. Same fix as mbedtls in tools/ci_fetch_deps.py?

    esp_hosted = TOP / "ports" / "espressif" / "esp-hosted"
    if (esp_hosted / ".gitmodules").exists():
        depth_maybe = "" if clone_supports_filter else "--depth 1"
        run(
            "Init esp-hosted nested submodules",
            f"git submodule update --init {filter_maybe} {depth_maybe} common/protobuf-c",
            cwd=esp_hosted,
        )