Re-structure sat-rs

- Add new shared subcrate satrs-shared to split off some shared
  components not expected to change very often.
- Renmame `satrs-core` to `satrs`. It is expected that sat-rs will remain
  the primary crate, so the core information is superfluous, and core also
  implies stability, which will not be the case for some time.

satrs-example/src/pus/stack.rs

@@ -1,4 +1,4 @@
-use satrs_core::pus::EcssTcInMemConverter;
+use satrs::pus::EcssTcInMemConverter;
 
 use super::{
     action::Pus8Wrapper, event::Pus5Wrapper, hk::Pus3Wrapper, scheduler::Pus11Wrapper,