Update embassy-time 0.3 -> 0.4

[ivmarkov]

@kedars

Minimal change that does only what the subject says.

However, very important because the change in embassy-time was of such a nature, that in your whole cargo tree you do need to have either embassy-time <= 0.3 or embassy-time >= 0.4 (but cannot have both).
(Basically, they changed their "time driver" API, which should not happen again any time soon.)

Since embassy-time is popular, and all crates depending on it are mass-updating to 0.4, we need to do it too, or else rs-matter cannot be used in one and the same project with these updated crates.

[semanticdiff-com]

Review changes with  

Changed Files

File	Status
README.md	Unsupported file format
rs-matter/Cargo.toml	Unsupported file format
rs-matter/tests/common/e2e/im/echo_cluster.rs	0% smaller

[ivmarkov]

Ready for review.