Add basic support for the EVM version Paris

This mostly means testing with evmone, but instruction renaming of difficulty->prevrandao is omitted.

test/libsolidity/semanticTests/state/block_difficulty.sol

@@ -5,6 +5,7 @@ contract C {
 }
 // ====
 // compileToEwasm: also
+// EVMVersion: <paris
 // ----
 // f() -> 200000000
 // f() -> 200000000

test/libsolidity/semanticTests/state/block_difficulty_post_paris.sol

@@ -0,0 +1,12 @@
+contract C {
+    function f() public returns (uint) {
+        return block.difficulty;
+    }
+}
+// ====
+// compileToEwasm: also
+// EVMVersion: >=paris
+// ----
+// f() -> 0xa86c2e601b6c44eb4848f7d23d9df3113fbcac42041c49cbed5000cb4f118777
+// f() -> 0xa86c2e601b6c44eb4848f7d23d9df3113fbcac42041c49cbed5000cb4f118777
+// f() -> 0xa86c2e601b6c44eb4848f7d23d9df3113fbcac42041c49cbed5000cb4f118777