samples: rust: add Rust I2C client registration sample

samples: rust: add Rust I2C client registration sample

Add a new `rust_i2c_client` sample, showing how to create a new
i2c client using `i2c::Registration`

Acked-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Igor Korotin <igor.korotin.linux@gmail.com>
Link: https://patch.msgid.link/20251116162210.171542-1-igor.korotin.linux@gmail.com
[ * Remove dependency to I2C_CHARDEV, depend on I2C=y.
  * Remove unnecessary impl Drop for SampleDriver.
  * Rename i2c::Registration, import Devres.
  * Fixup module description.
  * Add new source file to MAINTAINERS.
  - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>