Leetcode palindrome prime fasted solutions

Several solutions with 0ms execution time and benchmarks for prime-palindrome problem on leetcode.

Benchmark result

Benchmark_primePalindrome/letientai299-12         	   20000	     95646 ns/op	    1008 B/op	      29 allocs/op
Benchmark_primePalindrome/unknown-12              	    5000	    252136 ns/op	       0 B/op	       0 allocs/op
Benchmark_primePalindrome/tjucoder-12             	     500	   2118324 ns/op	  524816 B/op	   36900 allocs/op

• unknown guy's solution does zero allocation, and cool trick to generate palindrome with odds number of digits, but his solution need to check many more palindrome numbers than mine.
• tjucoder's solution works with string, thus require many more allocation and also his palindrome generation is not effective.
• Mine is currently the fastest thanks to: generate potental palindrome as list of int digits (so less allocation and conversion), filter out those palindrome that can't be prime.

If you have faster solutions, feel free to submit an MR. Note that:

• big.NewInt().ProbablyPrime() has terrible performance in the problem space (int). I got 4512 ms before switch to simple prime test up to sqrt(n).

Disclaimer

• I finish my solution without refer to either others solutions.
• This's for fun only (because I write quite a lot of code for this problems, so I want to know if it worth it). These code're not for production usage and I don't know if the performance of those solutions are still in above order if the problem space is bigger (from int to uint64 or big.Int).