vfmt: change all '$expr' to '${expr}' (#16428)

vlib/json/README.md

@@ -25,7 +25,7 @@ fn main() {
 	println(x)
 	//
 	s := json.encode(x)
-	println('Employee x: $s')
+	println('Employee x: ${s}')
 	assert s == '{"name":"Peter","age":28,"salary":95000.5,"title":2}'
 	//
 	y := json.decode(Employee, s)!

vlib/json/json_decode_with_optional_arg_test.v

@@ -15,5 +15,5 @@ fn test_json_decode_with_optional_arg() {
 fn print_info() !string {
 	dbconf := json.decode(DbConfig, os.read_file('dbconf.json')!)!
 	println(dbconf)
-	return '$dbconf'
+	return '${dbconf}'
 }

vlib/json/json_test.v

@@ -95,7 +95,7 @@ fn test_encode_decode_sumtype() {
 	enc := json.encode(game)
 	// eprintln('Encoded Game: $enc')
 
-	assert enc == '{"title":"Super Mega Game","player":{"name":"Monke","_type":"Human"},"other":[{"tag":"Pen","_type":"Item"},{"tag":"Cookie","_type":"Item"},1,"Stool",{"_type":"Time","value":$t.unix_time()}]}'
+	assert enc == '{"title":"Super Mega Game","player":{"name":"Monke","_type":"Human"},"other":[{"tag":"Pen","_type":"Item"},{"tag":"Cookie","_type":"Item"},1,"Stool",{"_type":"Time","value":${t.unix_time()}}]}'
 
 	dec := json.decode(SomeGame, enc)!
 	// eprintln('Decoded Game: $dec')
@@ -421,15 +421,15 @@ struct Info {
 fn test_decode_null_object() {
 	info := json.decode(Info, '{"id": 22, "items": null, "maps": null}')!
 	assert info.id == 22
-	assert '$info.items' == '[]'
-	assert '$info.maps' == '{}'
+	assert '${info.items}' == '[]'
+	assert '${info.maps}' == '{}'
 }
 
 fn test_decode_missing_maps_field() {
 	info := json.decode(Info, '{"id": 22, "items": null}')!
 	assert info.id == 22
-	assert '$info.items' == '[]'
-	assert '$info.maps' == '{}'
+	assert '${info.items}' == '[]'
+	assert '${info.maps}' == '{}'
 }
 
 struct Foo2 {