feat(websocket): add PSRAM allocation options

[gabsuren]

Add Kconfig options for PSRAM allocations in esp_websocket_client, including external-memory task stack gating with FREERTOS_TASK_CREATE_ALLOW_EXT_MEM.

Related

This PR builds on #980 and simplifies the external task-stack implementation.

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Note

Medium Risk
PSRAM task stacks impose cache-disabled constraints on WebSocket task and event-handler code; misconfiguration can cause subtle runtime faults, though options are off by default and failures fail closed without internal-RAM fallback.

Overview
Adds optional PSRAM placement for esp_websocket_client to reduce internal RAM use on SPIRAM-enabled builds.

ESP_WS_CLIENT_ALLOC_IN_EXT_RAM moves the main client object and its websocket_config_storage_t to PSRAM via heap_caps_calloc / heap_caps_free (no fallback—esp_websocket_client_init() returns NULL on failure). Other allocations (strings, RX/TX buffers, transports, mutexes, etc.) stay on internal RAM.

ESP_WS_CLIENT_TASK_STACK_IN_EXT_RAM creates the WebSocket worker with xTaskCreatePinnedToCoreWithCaps() so only the stack lives in PSRAM (TCB stays internal). The task exits with vTaskDeleteWithCaps(NULL); this path requires ESP-IDF ≥ 5.3.1 (compile-time #error otherwise). Failed stack allocation makes esp_websocket_client_start() return ESP_FAIL. Kconfig documents cache-off restrictions for code running on that task (including event handlers).

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