Add knobs to limit memories/tables in a Store

Fuzzing has turned up that module linking can create large amounts of
tables and memories in addition to instances. For example if N instances
are allowed and M tables are allowed per-instance, then currently
wasmtime allows MxN tables (which is quite a lot). This is causing some
wasm-smith-generated modules to exceed resource limits while fuzzing!

This commits adds corresponding `max_tables` and `max_memories`
functions to sit alongside the `max_instances` configuration.
Additionally fuzzing now by default configures all of these to a
somewhat low value to avoid too much resource usage while fuzzing.

crates/fuzzing/src/oracles.rs

@@ -101,6 +101,9 @@ pub fn instantiate_with_config(
         Ok(_) => {}
         // Allow traps which can happen normally with `unreachable`
         Err(e) if e.downcast_ref::<Trap>().is_some() => {}
+        // Allow resource exhaustion since this is something that our wasm-smith
+        // generator doesn't guarantee is forbidden.
+        Err(e) if e.to_string().contains("resource limit exceeded") => {}
         Err(e) => panic!("failed to instantiate {}", e),
     }
 }