Regenerate templated spec test files in Travis

[ShaneHarvey]

Various spec tests are generated via scripts. We should integrate these scripts with Travis to validate that the template files have been updated correctly.

Examples:

• Transaction tests: https://github.com/mongodb/specifications/blob/5b9cbb49a0e386a91da3b98d1a8cff3caaffaf17/source/transactions/tests/mongos-pin-auto-tests.py
• Client side encryption: https://github.com/mongodb/specifications/tree/5b9cbb49a0e386a91da3b98d1a8cff3caaffaf17/source/client-side-encryption/etc

[ShaneHarvey]

Note: I did this for the SDAM tests added in 371e95b:

     - name: "JSON regeneration check"
-      dist: trusty
-      language: node_js
-      node_js:
-        - 12
+      dist: xenial
+      language: python
+      python:
+        - 3.7
       install:
         - npm install -g js-yaml
       script:
+        - python3 ./source/server-discovery-and-monitoring/tests/errors/generate-error-tests.py
         - cd source && make && git diff --exit-code

We should still do the same for the transactions and encryption tests.

[blink1073]

This is done: https://github.com/mongodb/specifications/blob/3c7d132907d6f485f3abfbfa77103aaceceb94f6/.github/workflows/json-regenerate-check.yml