Introduce more appropriate assertion mechanism

rust-analyzer is a long-running program, so we *should* handle assertion
failures.

See also https://www.sqlite.org/assert.html.

crates/stdx/src/lib.rs

@@ -4,6 +4,8 @@ use std::{cmp::Ordering, ops, process, time::Instant};
 mod macros;
 pub mod panic_context;
 
+pub use crate::macros::{on_assert_failure, set_assert_hook};
+
 #[inline(always)]
 pub fn is_ci() -> bool {
     option_env!("CI").is_some()