reproduce starge gas metering behavior on exhaustion:

```
$ cd runtime/near-vm-runner
$ cargo test --release --lib -- tests::global_gas_test --exact --nocapture
   Compiling near-vm-runner v3.0.0 (/home/matklad/projects/nearcore/runtime/near-vm-runner)
    Finished release [optimized] target(s) in 4.11s
     Running /home/matklad/projects/nearcore/target/release/deps/near_vm_runner-f0eca327e6895b3d

running 1 test
cpu_ram_soak_test1: 125.684196ms FunctionCallError(HostError(GasLimitExceeded))
cpu_ram_soak_test2: 125.702125ms FunctionCallError(HostError(GasLimitExceeded))
cpu_ram_soak_test3: 125.205206ms FunctionCallError(HostError(GasLimitExceeded))
test tests::global_gas_test ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 61 filtered out; finished in 0.

$ cargo test --features protocol_feature_wasm_global_gas_counter --release --lib -- tests::global_gas_test --exact --nocapture
    Finished release [optimized] target(s) in 0.11s
     Running /home/matklad/projects/nearcore/target/release/deps/near_vm_runner-149fc9ad00e9397e

running 1 test
cpu_ram_soak_test1: 43.372139ms FunctionCallError(HostError(GasLimitExceeded))
cpu_ram_soak_test2: 431.044328ms FunctionCallError(HostError(GasLimitExceeded))
cpu_ram_soak_test3: 4.217799331s FunctionCallError(HostError(GasLimitExceeded))
test tests::global_gas_test ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 61 filtered out; finished in 4.76s
```

notice how in the second case the runtime increases. That's probably a
bug in the new gas metering. I suspect some integer overflow -- it only
manifests with 10^18 gas.

runtime/near-test-contracts/test-contract-rs/src/lib.rs

@@ -790,3 +790,42 @@ fn call_promise() {
         }
     }
 }
+
+#[no_mangle]
+pub unsafe fn cpu_ram_soak_test1() {
+    let mut buf = [0u8; 100 * 1024];
+    let len = buf.len();
+    for i in 0..10_000_000 {
+        let j = (i * 7 + len / 2) % len;
+        let k = (i * 3) % len;
+        let tmp = buf[k];
+        buf[k] = buf[j];
+        buf[j] = tmp;
+    }
+}
+
+#[no_mangle]
+pub unsafe fn cpu_ram_soak_test2() {
+    let mut buf = [0u8; 100 * 1024];
+    let len = buf.len();
+    for i in 0..100_000_000 {
+        let j = (i * 7 + len / 2) % len;
+        let k = (i * 3) % len;
+        let tmp = buf[k];
+        buf[k] = buf[j];
+        buf[j] = tmp;
+    }
+}
+
+#[no_mangle]
+pub unsafe fn cpu_ram_soak_test3() {
+    let mut buf = [0u8; 100 * 1024];
+    let len = buf.len();
+    for i in 0..1_000_000_000 {
+        let j = (i * 7 + len / 2) % len;
+        let k = (i * 3) % len;
+        let tmp = buf[k];
+        buf[k] = buf[j];
+        buf[j] = tmp;
+    }
+}

runtime/near-vm-runner/src/tests.rs

@@ -87,7 +87,7 @@ fn make_simple_contract_call_vm(
     method_name: &str,
     vm_kind: VMKind,
 ) -> (Option<VMOutcome>, Option<VMError>) {
-    make_simple_contract_call_with_gas_vm(code, method_name, 10u64.pow(14), vm_kind)
+    make_simple_contract_call_with_gas_vm(code, method_name, 10u64.pow(18), vm_kind)
 }
 
 fn make_cached_contract_call_vm(
@@ -118,3 +118,18 @@ fn make_cached_contract_call_vm(
         Some(cache),
     )
 }
+
+#[test]
+fn global_gas_test() {
+    let code = near_test_contracts::rs_contract();
+
+    // warmup.
+    make_simple_contract_call_with_gas_vm(code, "cpu_ram_soak_test1", 10_u64.pow(18), VMKind::Wasmer0);
+
+    let methods = ["cpu_ram_soak_test1", "cpu_ram_soak_test2", "cpu_ram_soak_test3"];
+    for &m in methods.iter() {
+        let t = std::time::Instant::now();
+        let (_out, err) = make_simple_contract_call_vm(code, m, VMKind::Wasmer0);
+        eprintln!("{}: {:?} {:?}", m, t.elapsed(), err.unwrap())
+    }
+}