fix(tests): update tests with new syntax

tests/cases/checker/04_custom_types.midas

@@ -1,6 +1,6 @@
-type Meter(float)
-type Second(float)
-type MeterPerSecond(float)
+type Meter = float
+type Second = float
+type MeterPerSecond = float
 
 extend Meter {
     op __add__(Meter) -> Meter

tests/cases/midas-parser/01_simple_types.midas

@@ -1,15 +1,15 @@
 // Simple custom type derived from float
-type Custom(float)
+type Custom = float
 
 // Simple custom types with constraints
-type Latitude(float) where (-90 <= _ <= 90)
-type Longitude(float) where (-180 <= _ <= 180)
+type Latitude = float where (-90 <= _ <= 90)
+type Longitude = float where (-180 <= _ <= 180)
 
 // Generic custom type (a Difference of T is derived from T, e.g. a difference of floats is a float
-type Difference[T](T)
+type Difference[T] = T
 
 // Complex custom type, containing two values accessible through properties
-type GeoLocation {
+type GeoLocation = {
     lat: Latitude
     lon: Longitude
 }
@@ -24,7 +24,7 @@ extend GeoLocation {
 
 // For complex generics, you need to specify how the genericity the properties
 // are handled
-type Difference[GeoLocation] {
+type Difference[GeoLocation] = {
     lat: Difference[Latitude]
     lon: Difference[Longitude]
 }
@@ -44,11 +44,11 @@ predicate StrictlyPositive(v: float) = v > 0
 predicate Equatorial(loc: GeoLocation) = (-10 <= loc.lat <= 10)
 predicate Arctic(loc: GeoLocation) = (loc.lat >= 66)
 
-type Person {
+type Person = {
     name: str
 
     // Property with an inline constraint
-    age: int? where (0 <= _ < 150)
+    age: None | (int where (0 <= _ < 150))
 
     // Property referencing a predicate
     height: float where StrictlyPositive