Merge bitcoin/bitcoin#23268: p2p: Use absolute FQDN for DNS seed domains

ca2c313aa2 Use absolute FQDN for DNS seed domains (Prayank)

Pull request description:

  Fixes https://github.com/bitcoin/bitcoin/issues/23193 by using absolute FQDN for domains used by DNS seeds.

  It improves security and should not break anything based on my research and testing. Few things about absolute FQDN are shared in https://superuser.com/questions/1467958/why-does-putting-a-dot-after-the-url-remove-login-information

  Master branch:

  ```
  DNS seed x9.dnsseed.bitcoin.dashjr.org. responded with IP 127.0.0.1
  ```

  PR branch:

  ```
  DNS seed x9.dnsseed.bitcoin.dashjr.org. responded with IP 159.89.108.149
  ```

  Reviewers can follow the steps mentioned in Issue to test: https://github.com/bitcoin/bitcoin/issues/23193#issuecomment-937717145

ACKs for top commit:
  practicalswift:
    cr ACK ca2c313aa2
  laanwj:
    code review ACK ca2c313aa2
  promag:
    Code review ACK ca2c313aa2.

Tree-SHA512: 9818227332282a78c45b4470c2fc80bf899ed78aed76644ebf014e0fff1b139402ea023acdea162363a478b6f6613dbf1da57e214d2240ea0f04310473f57cca

src/chainparams.cpp

@@ -118,15 +118,15 @@ public:
         // This is fine at runtime as we'll fall back to using them as an addrfetch if they don't support the
         // service bits we want, but we should get them updated to support all service bits wanted by any
         // release ASAP to avoid it where possible.
-        vSeeds.emplace_back("seed.bitcoin.sipa.be"); // Pieter Wuille, only supports x1, x5, x9, and xd
-        vSeeds.emplace_back("dnsseed.bluematt.me"); // Matt Corallo, only supports x9
-        vSeeds.emplace_back("dnsseed.bitcoin.dashjr.org"); // Luke Dashjr
-        vSeeds.emplace_back("seed.bitcoinstats.com"); // Christian Decker, supports x1 - xf
-        vSeeds.emplace_back("seed.bitcoin.jonasschnelli.ch"); // Jonas Schnelli, only supports x1, x5, x9, and xd
-        vSeeds.emplace_back("seed.btc.petertodd.org"); // Peter Todd, only supports x1, x5, x9, and xd
-        vSeeds.emplace_back("seed.bitcoin.sprovoost.nl"); // Sjors Provoost
-        vSeeds.emplace_back("dnsseed.emzy.de"); // Stephan Oeste
-        vSeeds.emplace_back("seed.bitcoin.wiz.biz"); // Jason Maurice
+        vSeeds.emplace_back("seed.bitcoin.sipa.be."); // Pieter Wuille, only supports x1, x5, x9, and xd
+        vSeeds.emplace_back("dnsseed.bluematt.me."); // Matt Corallo, only supports x9
+        vSeeds.emplace_back("dnsseed.bitcoin.dashjr.org."); // Luke Dashjr
+        vSeeds.emplace_back("seed.bitcoinstats.com."); // Christian Decker, supports x1 - xf
+        vSeeds.emplace_back("seed.bitcoin.jonasschnelli.ch."); // Jonas Schnelli, only supports x1, x5, x9, and xd
+        vSeeds.emplace_back("seed.btc.petertodd.org."); // Peter Todd, only supports x1, x5, x9, and xd
+        vSeeds.emplace_back("seed.bitcoin.sprovoost.nl."); // Sjors Provoost
+        vSeeds.emplace_back("dnsseed.emzy.de."); // Stephan Oeste
+        vSeeds.emplace_back("seed.bitcoin.wiz.biz."); // Jason Maurice
 
         base58Prefixes[PUBKEY_ADDRESS] = std::vector<unsigned char>(1,0);
         base58Prefixes[SCRIPT_ADDRESS] = std::vector<unsigned char>(1,5);
@@ -230,10 +230,10 @@ public:
         vFixedSeeds.clear();
         vSeeds.clear();
         // nodes with support for servicebits filtering should be at the top
-        vSeeds.emplace_back("testnet-seed.bitcoin.jonasschnelli.ch");
-        vSeeds.emplace_back("seed.tbtc.petertodd.org");
-        vSeeds.emplace_back("seed.testnet.bitcoin.sprovoost.nl");
-        vSeeds.emplace_back("testnet-seed.bluematt.me"); // Just a static list of stable node(s), only supports x9
+        vSeeds.emplace_back("testnet-seed.bitcoin.jonasschnelli.ch.");
+        vSeeds.emplace_back("seed.tbtc.petertodd.org.");
+        vSeeds.emplace_back("seed.testnet.bitcoin.sprovoost.nl.");
+        vSeeds.emplace_back("testnet-seed.bluematt.me."); // Just a static list of stable node(s), only supports x9
 
         base58Prefixes[PUBKEY_ADDRESS] = std::vector<unsigned char>(1,111);
         base58Prefixes[SCRIPT_ADDRESS] = std::vector<unsigned char>(1,196);
@@ -280,7 +280,7 @@ public:
 
         if (!args.IsArgSet("-signetchallenge")) {
             bin = ParseHex("512103ad5e0edad18cb1f0fc0d28a3d4f1f3e445640337489abb10404f2d1e086be430210359ef5021964fe22d6f8e05b2463c9540ce96883fe3b278760f048f5189f2e6c452ae");
-            vSeeds.emplace_back("seed.signet.bitcoin.sprovoost.nl");
+            vSeeds.emplace_back("seed.signet.bitcoin.sprovoost.nl.");
 
             // Hardcoded nodes can be removed once there are more DNS seeds
             vSeeds.emplace_back("178.128.221.177");