Spanner: rationalize 'all_types' round-trip systest (#6379)

* Expand 'all_types' table to include arrays of all types.

Use a separate 'pkey' column for the key, to make clear how null integer
values are normally used.

* Remove redundant query param bindings tests using 'all_types' table.

Add tableless tests for float bindings with transfinite values.

Add tableless tests for queries returning explicit transfinite values.

* Refactor round-trip test, 'all_types' data to make feature coverage clearar.

Author: tseaver

spanner/tests/_fixtures.py

@@ -29,15 +29,22 @@
     PRIMARY KEY (contact_id, phone_type),
     INTERLEAVE IN PARENT contacts ON DELETE CASCADE;
 CREATE TABLE all_types (
-    list_goes_on ARRAY<INT64>,
-    are_you_sure BOOL,
-    raw_data BYTES(16),
-    hwhen DATE,
-    approx_value FLOAT64,
-    eye_d INT64,
-    description STRING(16),
-    exactly_hwhen TIMESTAMP)
-    PRIMARY KEY (eye_d);
+    pkey INT64 NOT NULL,
+    int_value INT64,
+    int_array ARRAY<INT64>,
+    bool_value BOOL,
+    bool_array ARRAY<BOOL>,
+    bytes_value BYTES(16),
+    bytes_array ARRAY<BYTES(16)>,
+    date_value DATE,
+    date_array ARRAY<DATE>,
+    float_value FLOAT64,
+    float_array ARRAY<FLOAT64>,
+    string_value STRING(16),
+    string_array ARRAY<STRING(16)>,
+    timestamp_value TIMESTAMP,
+    timestamp_array ARRAY<TIMESTAMP>)
+    PRIMARY KEY (pkey);
 CREATE TABLE counters (
     name STRING(1024),
     value INT64 )