This replaces 'stack_smash' test, as it hasn't covered the respective area: it apparently just got compiled into 'unreachable' code and hasn't actually created stack frames (the actual VM stack overflow should fail with 'budget exceeded' error.
Also add observations for most of the hostile.rs tests (the only test not observed is too large/slow with observations).
What
This replaces 'stack_smash' test, as it hasn't covered the respective area: it apparently just got compiled into 'unreachable' code and hasn't actually created stack frames (the actual VM stack overflow should fail with 'budget exceeded' error.
Also add observations for most of the hostile.rs tests (the only test not observed is too large/slow with observations).
Resolves https://github.com/stellar/rs-soroban-env/issues/1156
Why
Improving test coverage
Known limitations
N/A