Add auto_reload functionality to timers

[faern]

Fixes #187

I did not expose setters or getters for the auto_reload value after creation. Having those would maybe be nicer, but I did not find any *_in_isr version for set_auto_reload and no non-in_isr version of get_auto_reload. So I ignored that for now. Having this in Config at least allows me to do what I want to do with the timers.

[faern]

I can't build and test this on master myself. I had to backport my commit to the v0.40.1 tag in order to test it. master just throws a bunch of these for me:

error[E0599]: no function or associated item named `from_infallible` found for struct `esp_idf_sys::EspError` in the current scope
   --> /home/faern/src/embedded/thirdparty/esp-idf-hal/src/i2c.rs:138:34
    |
138 |             return Err(EspError::from_infallible::<ESP_ERR_INVALID_ARG>());
    |                                  ^^^^^^^^^^^^^^^ function or associated item not found in `esp_idf_sys::EspError`

EDIT: Ah. from_infallible was added in esp-idf-sys 0.32.1. This crate has to up the lower bound on the dependency.