Switch PDM TX to the DAC mode. (#2134)

### What changed

Replaced:

* `I2S_PDM_TX_CLK_DEFAULT_CONFIG` → `I2S_PDM_TX_CLK_DAC_DEFAULT_CONFIG`
* `I2S_PDM_TX_SLOT_DEFAULT_CONFIG` → `I2S_PDM_TX_SLOT_DAC_DEFAULT_CONFIG`

These macros switch `line_mode` to `I2S_PDM_TX_ONE_LINE_DAC` and adjust other related fields.

### Why

PDM output sounded too high-pitched when using mono audio. I assume the point of `DriverPDM` is to simulate a DAC, and this config matches that better — especially compared to the old IDF 4 “legacy” driver. Audio now sounds correct.

Author: dkaukov

src/AudioTools/CoreAudio/AudioI2S/I2SESP32V1.h

@@ -351,7 +351,7 @@ class I2SDriverESP32V1 {
 
    protected:
     i2s_pdm_tx_slot_config_t getTxSlotConfig(I2SConfigESP32V1 &cfg) {
-      return I2S_PDM_TX_SLOT_DEFAULT_CONFIG(
+      return I2S_PDM_TX_SLOT_DAC_DEFAULT_CONFIG(
           (i2s_data_bit_width_t)cfg.bits_per_sample,
           (i2s_slot_mode_t)cfg.channels);
     }
@@ -363,7 +363,7 @@ class I2SDriverESP32V1 {
     }
 
     i2s_pdm_tx_clk_config_t getTxClockConfig(I2SConfigESP32V1 &cfg) {
-      return I2S_PDM_TX_CLK_DEFAULT_CONFIG((uint32_t)cfg.sample_rate);
+      return I2S_PDM_TX_CLK_DAC_DEFAULT_CONFIG((uint32_t)cfg.sample_rate);
     }
 
     bool startTX(I2SConfigESP32V1 &cfg, i2s_chan_handle_t &tx_chan, int txPin) {
@@ -603,4 +603,4 @@ using I2SDriver = I2SDriverESP32V1;
 
 }  // namespace audio_tools
 
-#endif
+#endif