fix(wasm): add common definitions to stdlib (#5199) (#5208)

Also expose `strlen` through `string.h` instead of `stdio.h`.

(cherry picked from commit f4ca3d95ca)

Co-authored-by: Trim21 <trim21.me@gmail.com>

crates/language/wasm/include/string.h

@@ -13,4 +13,6 @@ void *memset(void *dst, int value, size_t count);
 
 int strncmp(const char *left, const char *right, size_t n);
 
+size_t strlen(const char *str);
+
 #endif // TREE_SITTER_WASM_STRING_H_