Merge bitcoin/bitcoin#24213: refactor: use Span in random.*

3ae7791bca refactor: use Span in random.* (pasta)

Pull request description:

  ~This PR does two things~
  1. use a Span<unsigned char> for GetRandBytes and GetStrongRandBytes

  ~2. make GetRand a template for which any integral type can be used, where the default behavior is to return a random integral up to the max of the integral unless a max is provided.
  This simplifies a lot of code from `GetRand(std::numeric_limits<uint64_t>::max()` -> `GetRand<uint64_t>()`~

  MarcoFalke this was inspired by your comment here: https://github.com/bitcoin/bitcoin/pull/24185#issuecomment-1025514263 about using Span, so hopefully I'll be able to get this PR done and merged 😂

  ~Also, if requested I could revert the `GetRand(std::numeric_limits<uint64_t>::max()` -> `GetRand<uint64_t>()` related changes if it ends up causing too many conflicts~

ACKs for top commit:
  laanwj:
    Thank you! Code review re-ACK 3ae7791bca

Tree-SHA512: 12375a83b68b288916ba0de81cfcab4aac14389a66a36811ae850427435eb67dd55e47df9ac3ec47db4e214f4330139e548bec815fff8a3f571484ea558dca79

src/wallet/test/wallet_crypto_tests.cpp

@@ -81,7 +81,7 @@ BOOST_AUTO_TEST_CASE(passphrase) {
 
     std::string hash(GetRandHash().ToString());
     std::vector<unsigned char> vchSalt(8);
-    GetRandBytes(vchSalt.data(), vchSalt.size());
+    GetRandBytes(vchSalt);
     uint32_t rounds = InsecureRand32();
     if (rounds > 30000)
         rounds = 30000;