feat(newlib): riscv: add CONFIG_LIBC_OPTIMIZED_MISALIGNED_ACCESS config option

This option replaces implementations of functions from ROM:
  - memcpy
  - memcmp
  - memmove
  - str[n]cpy
  - str[n]cmp

The functions used in the firmware will be better optimized for misaligned
memory. Here are some measurements in CPU cycles for 4096-byte buffers:

  memcpy:  28676 -> 4128
  memcmp:  49147 -> 14259
  memmove: 33896 -> 8086
  strcpy:  32771 -> 17313
  strcmp:  32775 -> 13191

components/newlib/src/string/memcmp.c

@@ -0,0 +1,59 @@
+/*
+ * SPDX-FileCopyrightText: 1994-2009 Red Hat, Inc.
+ *
+ * SPDX-License-Identifier: BSD-2-Clause-FreeBSD AND Apache-2.0
+ *
+ * SPDX-FileContributor: 2025 Espressif Systems (Shanghai) CO LTD
+ */
+#include <string.h>
+#include "local.h"
+
+__attribute__((optimize("-Os")))
+int
+memcmp(const void *m1,
+       const void *m2,
+       size_t n)
+{
+    unsigned char *s1 = (unsigned char *) m1;
+    unsigned char *s2 = (unsigned char *) m2;
+    unsigned long *a1;
+    unsigned long *a2;
+
+    /* If the size is too small, or either pointer is unaligned,
+       then we punt to the byte compare loop.  Hopefully this will
+       not turn up in inner loops.  */
+    if (!TOO_SMALL_LITTLE_BLOCK(n) && !UNALIGNED_X_Y(s1, s2)) {
+        /* Otherwise, load and compare the blocks of memory one
+           word at a time.  */
+        a1 = (unsigned long*) s1;
+        a2 = (unsigned long*) s2;
+        while (!TOO_SMALL_LITTLE_BLOCK(n)) {
+            if (*a1 != *a2) {
+                break;
+            }
+            a1++;
+            a2++;
+            n -= LITTLE_BLOCK_SIZE;
+        }
+
+        /* check m mod LITTLE_BLOCK_SIZE remaining characters */
+
+        s1 = (unsigned char*)a1;
+        s2 = (unsigned char*)a2;
+    }
+
+    while (n--) {
+        if (*s1 != *s2) {
+            return *s1 - *s2;
+        }
+        s1++;
+        s2++;
+    }
+
+    return 0;
+}
+
+// Hook to force the linker to include this file
+void esp_libc_include_memcmp_impl(void)
+{
+}