Implement most of the builtin time module (#82)

* Implement builtin `time.add_date` method

* Implement builtin `time.clock` method

* Implement builtin `time.date` method

* Implement builtin `time.diff` method

* Implement builtin `time.format` method

* Migrate `time.now_ns` to `chrono`

* Implement builtin `time.parse_ns` method

* Implement builtin `time.parse_rfc3339_ns` method

* Implement builtin `time.weekday` method

* Add conditional `test` module for OPA tests

* Cache result of `time.now_ns`

* Fail in strict mode if timestamp is outside of range

* Add `ensure_i32` util

* Move `diff_between_datetimes` into its own file and include appropriate license

tests/interpreter/cases/builtins/time/diff.yaml

@@ -0,0 +1,64 @@
+# Copyright (c) Microsoft Corporation.
+# Licensed under the MIT License.
+
+cases:
+  - note: without-timezone
+    data: {}
+    modules:
+      - |
+        package test
+
+        a := time.diff(1703444325734390000, 1257894000000000000)
+    query: data.test
+    want_result:
+      a: 
+        - 14
+        - 1
+        - 13
+        - 19
+        - 58
+        - 45
+
+  - note: with-timezone
+    data: {}
+    modules:
+      - |
+        package test
+
+        a := time.diff([1703444325734390000, "UTC"], [1257894000000000000, ""])
+    query: data.test
+    want_result:
+      a: 
+        - 14
+        - 1
+        - 13
+        - 19
+        - 58
+        - 45
+
+  - note: tz1-greater-than-tz2
+    data: {}
+    modules:
+      - |
+        package test
+
+        a := time.diff(1257894000000000000, 1703444325734390000)
+    query: data.test
+    want_result:
+      a: 
+        - 14
+        - 1
+        - 13
+        - 19
+        - 58
+        - 45
+
+  - note: invalid-type
+    data: {}
+    modules:
+      - |
+        package test
+
+        a := time.diff("1703444325734390000", 1257894000000000000)
+    query: data.test
+    error: '`time.diff` expects `ns` to be a `number` or `array[number, string]`. Got `"1703444325734390000"` instead'