stacktrace: Search through context for a valid location

[djolertrk]

Before this PR, the test from 0xMiden/compiler#810 looks as:

Stack Trace:
 `-> root_ns:[email protected]::init in <unavailable>:

Last 5 Instructions (of current frame):
 |   drop
 |   eq
 |   not
 |   drop
 |   pad
 `-> <error occured here>


Last 5 Instructions (any frame):
 |   end
 |   split
 |   span
 |   drop
 |   pad
 `-> <error occured here>


Last Known State (at most recent instruction which succeeded):
 | Operand Stack: [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
 
Error:   x Main thread panicked.
  |-> at tests/integration/src/rust_masm_tests/debug_source_locations.rs:70:18
  `->   × program execution failed at step 184 (cycle 183): assertion failed at clock cycle 183 with error code: 0

after this workaround, it is:

Stack Trace:
 `-> root_ns:[email protected]::init in /Users/djtodorovic/projects/crypto/MIDEN/compiler/tests/rust-apps-wasm/rust-sdk/assert-debug-test/src/lib.rs:26:13:

Last 5 Instructions (of current frame):
 |   drop
 |   eq
 |   not
 |   drop
 |   pad
 `-> <error occured here>


Last 5 Instructions (any frame):
 |   end
 |   split
 |   span
 |   drop
 |   pad
 `-> <error occured here>


Last Known State (at most recent instruction which succeeded):
 | Operand Stack: [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
 
Error:   x Main thread panicked.
  |-> at tests/integration/src/rust_masm_tests/debug_source_locations.rs:70:18
  `->   × program execution failed at step 184 (cycle 183): assertion failed at clock cycle 183 with error code: 0
          ╭─[/Users/djtodorovic/projects/crypto/MIDEN/compiler/tests/rust-apps-wasm/rust-sdk/assert-debug-test/src/lib.rs:26:13]
       25 │ pub fn entrypoint(x: u32) -> u32 {
       26 │     assert!(x > 100);
          ·             ▲
       27 │     x
          ╰────

[djolertrk]

cc @greenhat @bitwalker

[bitwalker]

@djolertrk If you sign your commit and force push, I'll get this merged