Use new interrupt allocator

[MartyMacGyver]

As recommended in this discussion:

• https://esp32.com/viewtopic.php?p=5110#p5110

Migrate to the new interrupt allocator:

• intr_matrix_set() --> esp_intr_alloc() (verify this)
• OLD: esp-idf/components/esp32/include/rom/ets_sys.h
• NEW: esp-idf/components/esp32/include/esp_intr_alloc.h
• https://github.com/espressif/esp-idf/blob/master/docs/api/system/intr_alloc.rst#multicore-issues
• Similar change: https://www.esp32.com/viewtopic.php?t=380&start=20

[MartyMacGyver]

intr_matrix_set(xPortGetCoreID(), ETS_RMT_INTR_SOURCE, ETS_RMT_CTRL_INUM);
ESP_RMT_CTRL_INTRL(ws2812_handleInterrupt, NULL);
...
ESP_INTR_ENABLE(ETS_RMT_CTRL_INUM);

after macro expansion becomes

intr_matrix_set(xPortGetCoreID(), ETS_RMT_INTR_SOURCE, ETS_RMT_CTRL_INUM);
xt_set_interrupt_handler(ETS_RMT_CTRL_INUM, ws2812_handleInterrupt, NULL)
...
xt_ints_on(1<<ETS_RMT_CTRL_INUM)

tweaked with BIT macro becomes

intr_matrix_set(xPortGetCoreID(), ETS_RMT_INTR_SOURCE, ETS_RMT_CTRL_INUM);
xt_set_interrupt_handler(ETS_RMT_CTRL_INUM, ws2812_handleInterrupt, NULL)
...
#define BIT(x) (1 << (x))
xt_ints_on(BIT(ETS_RMT_CTRL_INUM))

in new interrupt scheme should become:

esp_intr_alloc(ETS_RMT_INTR_SOURCE, 0, ws2812_handleInterrupt, NULL, rmt_intr_handle);

• xPortGetCoreID() should be superfluous - per docs: "The interrupt will always be allocated on the core that runs this function"
• This allocates AND enables the interrupt.
• Not sure how ETS_RMT_CTRL_INUM goes away here but it appears to.

esp_intr_enable()/esp_intr_enable() on intr_handle_t *rmt_intr_handle should work (or set that param to NULL if always on).