Improve full_join.rs: move has_multi_equal out of loop

[xumingming]

currently has_multi_equal is repeated set in loops, which is not necessary:

auron/native-engine/datafusion-ext-plans/src/joins/smj/full_join.rs

Lines 134 to 154 in 832b9b7

	let mut has_multi_equal = false;
	let mut l_equal = true;
	let mut r_equal = true;
	while l_equal && r_equal {
	if l_equal {
	l_equal = !cur1.finished() && cur1.cur_key() == cur1.key(l_key_idx);
	if l_equal {
	has_multi_equal = true;
	equal_lindices.push(cur1.cur_idx());
	cur_forward!(cur1);
	}
	}
	if r_equal {
	r_equal = !cur2.finished() && cur2.cur_key() == cur2.key(r_key_idx);
	if r_equal {
	has_multi_equal = true;
	equal_rindices.push(cur2.cur_idx());
	cur_forward!(cur2);
	}
	}
	}