[lib] Move some ZSTD_CCtx_params off the stack

* Take `params` by const reference in `ZSTD_resetCCtx_internal()`.
* Add `simpleApiParams` to the CCtx and use them in the simple API
  functions, instead of creating those parameters on the stack.

I think this is a good direction to move in, because we shouldn't need
to worry about adding parameters to `ZSTD_CCtx_params`, since it should
always be on the heap (unless they become absoultely gigantic).

Some `ZSTD_CCtx_params` are still on the stack in the CDict functions,
but I've left them for now, because it was a little more complex, and we
don't use those functions in stack-constrained currently.

lib/compress/zstd_compress_internal.h

@@ -340,6 +340,7 @@ struct ZSTD_CCtx_s {
     int bmi2;                            /* == 1 if the CPU supports BMI2 and 0 otherwise. CPU support is determined dynamically once per context lifetime. */
     ZSTD_CCtx_params requestedParams;
     ZSTD_CCtx_params appliedParams;
+    ZSTD_CCtx_params simpleApiParams;    /* Param storage used by the simple API - not sticky. Must only be used in top-level simple API functions for storage. */
     U32   dictID;
     size_t dictContentSize;