feat: Support float4 in JDBC (googleapis#2336)

Author: sakthivelmanii

java-spanner-jdbc/src/main/java/com/google/cloud/spanner/jdbc/JdbcDataType.java

@@ -113,6 +113,8 @@ public Type getSpannerType() {
     }
   },
   FLOAT32 {
+    private final Set<String> aliases = new HashSet<>(Collections.singletonList("float4"));
+
     @Override
     public int getSqlType() {
       return Types.REAL;
@@ -152,6 +154,11 @@ public List<Float> getArrayElements(ResultSet rs, int columnIndex) {
     public Type getSpannerType() {
       return Type.float32();
     }
+
+    @Override
+    public Set<String> getPostgreSQLAliases() {
+      return aliases;
+    }
   },
   FLOAT64 {
     private final Set<Class<?>> classes = new HashSet<>(Arrays.asList(Float.class, Double.class));