chore(schema): move serde functions from smithy-client to core/serde (#1594)

Author: kuhe

.changeset/wild-rice-love.md

@@ -0,0 +1,6 @@
+---
+"@smithy/smithy-client": minor
+"@smithy/core": minor
+---
+
+move serde functions from smithy-client to core/serde

packages/smithy-client/src/date-utils.spec.ts renamed to packages/core/src/submodules/serde/date-utils.spec.ts

@@ -1 +1,7 @@
+export * from "./parse-utils";
+export * from "./date-utils";
+export * from "./quote-header";
+export * from "./split-header";
 export * from "./value/NumericValue";
+export * from "./lazy-json";
+export * from "./split-every";