Extend fuzzing set up

Adds a parse function ins `jv_parse.c` that enables parsing using custom
flags for the parser. This is then used by two fuzzers added as well.

This is to make sure fuzzing hits various code parts currently not
fuzzed, e.g. `stream_token`:
https://storage.googleapis.com/oss-fuzz-coverage/jq/reports/20231125/linux/src/jq/src/jv_parse.c.html#L241

Signed-off-by: David Korczynski <david@adalogics.com>

tests/jq_fuzz_parse_extended.c

@@ -0,0 +1,29 @@
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "jv.h"
+
+int LLVMFuzzerTestOneInput(uint8_t *data, size_t size) {
+  if (size < 4) {
+    return 0;
+  }
+
+  int fuzz_flags = *(int*)data;
+  data += 4;
+  size -= 4;
+
+  // Creat null-terminated string
+  char *null_terminated = (char *)malloc(size + 1);
+  memcpy(null_terminated, (char *)data, size);
+  null_terminated[size] = '\0';
+
+  // Fuzzer entrypoint
+  jv res = jv_parse_custom_flags(null_terminated, fuzz_flags);
+  jv_free(res);
+  
+  // Free the null-terminated string
+  free(null_terminated);
+
+  return 0;
+}

tests/jq_fuzz_parse_stream.c

@@ -0,0 +1,21 @@
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "jv.h"
+
+int LLVMFuzzerTestOneInput(uint8_t *data, size_t size) {
+  // Creat null-terminated string
+  char *null_terminated = (char *)malloc(size + 1);
+  memcpy(null_terminated, (char *)data, size);
+  null_terminated[size] = '\0';
+
+  // Fuzzer entrypoint
+  jv res = jv_parse_custom_flags(null_terminated, JV_PARSE_STREAMING);
+  jv_free(res);
+  
+  // Free the null-terminated string
+  free(null_terminated);
+
+  return 0;
+}