feat(uart): [IDF5.1] fixes HardwareSerial::updateBaudRate() using a baud rate higher 230400 - checks UART Clock Source

[SuGlider]

EXCLUSIVE FOR IDF 5.1 - Arduino Core 3.0.x

Description of Change

ESP32 and ESP32S2 use REF_TICK as UART clock source whenever the baud rate is lower then 250,000.
This is done within HardwareSerial::begin(uint32_t baud)
This prevents issues with chaning the APB clock to lower than 40MHz, specially when achieving lower power consumpition.

This PR also fixes it for the HardwareSerial::updateBaudRate(uint32_t baud) by checking the target baud rate and adjusting the UART Clock Source that will make it work correctly.

Tests scenarios

Using this sketch (from the issue report) using ESP32 and ESP32S2

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  delay(500);
  
  Serial1.begin(230400);
  Serial.printf("%d\n", Serial1.baudRate());
  // Clock is now UART_SCLK_REF_TICK

  Serial1.updateBaudRate(460800);
  Serial.printf("%d\n", Serial1.baudRate());
  // Clock is still UART_SCLK_REF_TICK

  Serial1.end();
  Serial1.begin(460800);
  Serial.printf("%d\n", Serial1.baudRate());
  // Clock is now UART_SCLK_APB <<---- FIXED by the PR
}

void loop() {
}

Related links

Closes #10641

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Test Results

 56 files   56 suites   4m 21s ⏱️
 21 tests  21 ✅ 0 💤 0 ❌
134 runs  134 ✅ 0 💤 0 ❌

Results for commit a509e2b.