Add fast reading function and refactor read_channel methods for HX711

[supcik]

This pull request addresses the issue #7.

I made a separated function read_fast for the bit banging reading of the AD. This improved the performance by caching the object reference and opens up possibilities for other implementations.

The delays are enforced with the microcontroller.delay_us function.

I had to disable the interrupts during the read, because according to the datasheet, the clock is not allowed to stay up for more than 50µs during the operation :

With interrupts on, I was not able to guarantee the correct timing.

I tested on a ESP32 and it never failed.

Note that some other lines have been reformated according to the style guide defined in ruff.toml (line-length = 100)