feat(uart): simplifies UART example based on MODBUS standard

[SuGlider]

Description of Change

Improves and simplifies the Serial OnReceive example.
The example uses Rx Timeout based on MODBUS standard.

This change will demonstrate how to receive any number of bytes and then execute a callback as soon as defined timeout happens.

Tests scenarios

Using this example with ESP32, ESP32-S2, ESP32-S3, ESP32-C3 and ESP32-C6.

Related links

None.

[github-actions]

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[Copilot]

Pull Request Overview

This PR simplifies the UART onReceive example by updating documentation and modifying how received data is handled in order to align with the MODBUS standard.

• Updated callback comments and behavior to reflect onlyOnTimeout usage
• Removed semaphore protection in favor of a simplified while loop for reading available data
• Adjusted setup configurations and reduced the main loop delay to better demonstrate rapid processing

Comments suppressed due to low confidence (1)

libraries/ESP32/examples/Serial/onReceiveExample/onReceiveExample.ino:112

• [nitpick] The main loop delay has been reduced from 1000 ms to 1 ms, which may lead to excessive CPU usage and frequent serial prints. Verify that this rapid polling is intentional for the example's demonstration of RX Timeout behavior.

delay(1); 

[github-actions]

Memory usage test (comparing PR against master branch)

The table below shows the summary of memory usage change (decrease - increase) in bytes and percentage for each target.

Memory	FLASH [bytes]		FLASH [%]		RAM [bytes]		RAM [%]
Target	DEC	INC	DEC	INC	DEC	INC	DEC	INC
ESP32P4	💚 -68	0	💚 -0.02	0.00	0	0	0.00	0.00
ESP32S3	💚 -84	0	💚 -0.03	0.00	0	0	0.00	0.00
ESP32S2	💚 -16	0	💚 -0.01	0.00	0	0	0.00	0.00
ESP32C3	💚 -90	0	💚 -0.03	0.00	0	0	0.00	0.00
ESP32C6	💚 -66	0	💚 -0.03	0.00	0	0	0.00	0.00
ESP32H2	💚 -88	0	💚 -0.03	0.00	0	0	0.00	0.00
ESP32	0	0	0.00	0.00	0	0	0.00	0.00

Click to expand the detailed deltas report [usage change in BYTES]

Target	ESP32P4		ESP32S3		ESP32S2		ESP32C3		ESP32C6		ESP32H2		ESP32
Example	FLASH	RAM	FLASH	RAM	FLASH	RAM	FLASH	RAM	FLASH	RAM	FLASH	RAM	FLASH	RAM
libraries/ESP32/examples/Serial/onReceiveExample	💚 -68	0	💚 -84	0	💚 -16	0	💚 -90	0	💚 -66	0	💚 -88	0	0	0

[lucasssvaz]

LGTM