Double the default allowed table elements

This commit doubles the default allowed table elements per table in the
pooling allocator from 10k to 20k. This helps to, by default, run the
module produced in bytecodealliance#8504.

crates/wasmtime/src/runtime/vm/instance/allocator/pooling.rs

@@ -156,7 +156,9 @@ impl Default for InstanceLimits {
             total_stacks: 1000,
             core_instance_size: 1 << 20, // 1 MiB
             max_tables_per_module: 1,
-            table_elements: 10_000,
+            // NB: in #8504 it was seen that a C# module in debug module can
+            // have 10k+ elements.
+            table_elements: 20_000,
             max_memories_per_module: 1,
             memory_pages: 160,
             #[cfg(feature = "gc")]