Removes context parameter from instruction-scoped operations (#923)

We originally had a `context.Context` for anything that might be
traced, but it turned out to be only useful for lifecycle and host functions.

For instruction-scoped aspects like memory updates, a context parameter is too
fine-grained and also invisible in practice. For example, most users will use
the compiler engine, and its memory, global or table access will never use go's
context.

Signed-off-by: Adrian Cole <adrian@tetrate.io>

internal/wasm/store_test.go

@@ -82,7 +82,7 @@ func TestModuleInstance_Memory(t *testing.T) {
 
 			mem := instance.ExportedMemory("memory")
 			if tc.expected {
-				require.Equal(t, tc.expectedLen, mem.Size(testCtx))
+				require.Equal(t, tc.expectedLen, mem.Size())
 			} else {
 				require.Nil(t, mem)
 			}