Add bitamp_to_string function (#2731)

This CL changes:

1. add function bitmap_to_string and bitmap_from_string, which will
 convert a bitmap to/from string which contains all bit in bitmap
2. add function murmur_hash3_32, which will compute murmur hash for
input strings
3. make the function cast float to string the same with user result
logic

be/src/exprs/bitmap_function.cpp

@@ -20,6 +20,8 @@
 #include "exprs/anyval_util.h"
 #include "util/bitmap.h"
 #include "util/string_parser.hpp"
+#include "gutil/strings/split.h"
+#include "gutil/strings/numbers.h"
 
 namespace doris {
 
@@ -425,7 +427,40 @@ StringVal BitmapFunctions::bitmap_and(FunctionContext* ctx, const StringVal& lhs
         bitmap.intersect(RoaringBitmap((char*)rhs.ptr));
     }
 
-    StringVal result(ctx,bitmap.size());
+    StringVal result(ctx, bitmap.size());
+    bitmap.serialize((char*)result.ptr);
+    return result;
+}
+
+StringVal BitmapFunctions::bitmap_to_string(FunctionContext* ctx, const StringVal& input) {
+    if (input.is_null) {
+        return StringVal::null();
+    }
+    RoaringBitmap bitmap_obj;
+    RoaringBitmap* bitmap = &bitmap_obj;
+    if (input.len == 0) {
+        bitmap = (RoaringBitmap*)input.ptr;
+    } else {
+        bitmap_obj.deserialize((const char*)input.ptr);
+    }
+
+    std::string str = bitmap->to_string();
+    return AnyValUtil::from_string_temp(ctx, str);
+}
+
+StringVal BitmapFunctions::bitmap_from_string(FunctionContext* ctx, const StringVal& input) {
+    if (input.is_null) {
+        return StringVal::null();
+    }
+
+    std::vector<uint32_t> bits;
+    if (!SplitStringAndParse({(const char*)input.ptr, input.len}, ",", &safe_strtou32, &bits)) {
+        return StringVal::null();
+    }
+
+    RoaringBitmap bitmap(bits);
+
+    StringVal result(ctx, bitmap.size());
     bitmap.serialize((char*)result.ptr);
     return result;
 }