Fix mbed not using REFRESH_INTERVAL

[razvanphp]

This pull request refactors the Servo library for mbed-based boards to utilize std::chrono durations instead of manual conversions with floating-point numbers. The 20ms interval was hardcoded for mbed platform only.

Changes:

• Fix bug on mbed platform of not using REFRESH_INTERVAL at all
• Modified ServoImpl::start() and ServoImpl::call() to use std::chrono::microseconds.
• Eliminated floating-point divisions by 0.02f (hardcoded) and 1e6.
• Ensured backward compatibility by keeping existing functionality intact.

Benefits:

• Enhanced type safety and precision.
• Simplified codebase and aligned with other platforms.
• Facilitates dynamic adjustment of REFRESH_INTERVAL.

Testing:

• Verified functionality with default REFRESH_INTERVAL of 20000 microseconds.
• Tested with REFRESH_INTERVAL set to 10000 and 5000 microseconds.
• Confirmed correct servo operation and signal timing using an oscilloscope.

Notes:

This change aligns the Servo library with the updated mbed OS API that favours std::chrono durations since mbedOS 6.0.0, see

https://github.com/arduino/ArduinoCore-mbed/blob/702daa02e244fb8710b48599f38786a67c590699/cores/arduino/mbed/drivers/include/drivers/Ticker.h#L85-L122

[github-actions]

Memory usage change @ fab0609

Board	flash	%	RAM for global variables	%
arduino:avr:leonardo	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:avr:mega	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:avr:nano	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:mbed_nano:nano33ble	💚 -448 - -448	-0.05 - -0.05	0 - 0	0.0 - 0.0
arduino:mbed_nano:nanorp2040connect	💚 -1868 - -1868	-0.01 - -0.01	0 - 0	0.0 - 0.0
arduino:mbed_portenta:envie_m7	N/A	N/A	N/A	N/A
arduino:mbed_portenta:envie_m7:target_core=cm4	N/A	N/A	N/A	N/A
arduino:megaavr:nona4809	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:sam:arduino_due_x_dbg	0 - 0	0.0 - 0.0	N/A	N/A
arduino:samd:mkrzero	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0

Click for full report table

Board	examples/Knob flash	%	examples/Knob RAM for global variables	%	examples/Sweep flash	%	examples/Sweep RAM for global variables	%
arduino:avr:leonardo	0	0.0	0	0.0	0	0.0	0	0.0
arduino:avr:mega	0	0.0	0	0.0	0	0.0	0	0.0
arduino:avr:nano	0	0.0	0	0.0	0	0.0	0	0.0
arduino:mbed_nano:nano33ble	-448	-0.05	0	0.0	-448	-0.05	0	0.0
arduino:mbed_nano:nanorp2040connect	-1868	-0.01	0	0.0	-1868	-0.01	0	0.0
arduino:mbed_portenta:envie_m7	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
arduino:mbed_portenta:envie_m7:target_core=cm4	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
arduino:megaavr:nona4809	0	0.0	0	0.0	0	0.0	0	0.0
arduino:sam:arduino_due_x_dbg	0	0.0	N/A	N/A	0	0.0	N/A	N/A
arduino:samd:mkrzero	0	0.0	0	0.0	0	0.0	0	0.0

Click for full report CSV

Board,examples/Knob<br>flash,%,examples/Knob<br>RAM for global variables,%,examples/Sweep<br>flash,%,examples/Sweep<br>RAM for global variables,%
arduino:avr:leonardo,0,0.0,0,0.0,0,0.0,0,0.0
arduino:avr:mega,0,0.0,0,0.0,0,0.0,0,0.0
arduino:avr:nano,0,0.0,0,0.0,0,0.0,0,0.0
arduino:mbed_nano:nano33ble,-448,-0.05,0,0.0,-448,-0.05,0,0.0
arduino:mbed_nano:nanorp2040connect,-1868,-0.01,0,0.0,-1868,-0.01,0,0.0
arduino:mbed_portenta:envie_m7,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A
arduino:mbed_portenta:envie_m7:target_core=cm4,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A
arduino:megaavr:nona4809,0,0.0,0,0.0,0,0.0,0,0.0
arduino:sam:arduino_due_x_dbg,0,0.0,N/A,N/A,0,0.0,N/A,N/A
arduino:samd:mkrzero,0,0.0,0,0.0,0,0.0,0,0.0

[CLAassistant]

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