Increase stack size to 16MB

Default is 8MB. As we start both Alice and bob in test, it is fine to
double the stack size but still assume it does not impact the
normal execution of the binary.

.github/workflows/ci.yml

@@ -105,7 +105,7 @@ jobs:
         run: cargo +nightly test --workspace --all-features -- -Z unstable-options --report-time
         env:
           MONERO_ADDITIONAL_SLEEP_PERIOD: 60000
-          RUST_MIN_STACK: 10000000
+          RUST_MIN_STACK: 16777216 # 16 MB. Default is 8MB. This is fine as in tests we start 2 programs: Alice and Bob.
 
       - name: Build binary
         run: |