I2C: Generally, follow common "good practices" and idiomatic Rust style

[bugadani]

We have commented-out code, at least one FIXME and TODO in the codebase.

[tom-borcin]

Investigate if FIXME and TODO are user facing

[bjoernQ]

FIXME

In Driver:::setup

        // Configure filter
        // FIXME if we ever change this we need to adapt `set_frequency` for ESP32
        set_filter(self.register_block(), Some(7), Some(7));

In set_frequency (ESP32)

        // FIXME since we always set the filter threshold to 7 we don't need conditional
        // code here once that changes we need the conditional code here
        scl_high -= 7 + 6;

    #[cfg(not(any(esp32, esp32s2)))]
    /// Reads all bytes from the RX FIFO.
    fn read_all_from_fifo_blocking(&self, buffer: &mut [u8]) -> Result<(), Error> {
        // Read bytes from FIFO
        // FIXME: Handle case where less data has been provided by the slave than
        // requested? Or is this prevented from a protocol perspective?
        for byte in buffer.iter_mut() {
...

#[cfg(any(esp32, esp32s2))]
    /// Reads all bytes from the RX FIFO.
    fn read_all_from_fifo_blocking(&self, buffer: &mut [u8]) -> Result<(), Error> {
...
        // Read bytes from FIFO
        // FIXME: Handle case where less data has been provided by the slave than
        // requested? Or is this prevented from a protocol perspective?
        for byte in buffer.iter_mut() {
...

TODO

In config

    // TODO: when supporting interrupts, document that SCL = high also triggers an interrupt.
    pub timeout: Option<u32>,

    // TODO: missing interrupt APIs

[MabezDev]

I don't think these are user facing issues worth blocking on. It seems timeout will be resolved by #2864