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/generators.rs

@@ -75,7 +75,7 @@ pub struct Config {
 impl Config {
     /// Converts this to a `wasmtime::Config` object
     pub fn to_wasmtime(&self) -> wasmtime::Config {
-        let mut cfg = wasmtime::Config::new();
+        let mut cfg = crate::fuzz_default_config(wasmtime::Strategy::Auto).unwrap();
         cfg.debug_info(self.debug_info)
             .static_memory_maximum_size(self.static_memory_maximum_size.unwrap_or(0).into())
             .static_memory_guard_size(self.static_memory_guard_size.unwrap_or(0).into())