[Core] Bug fix for Tag Values representing booleans being loaded as boolean instead of strings

[JGSweets]

This PR updates jinja2 ray templates for gcp and aws when utilizing Tags.
Currently, boolean strings are inserted into the Ray YAML without being escaped. This fixes that by using the builtin tojson function for jinja2.

Otherwise, tags which had the values: false or true would fail to launch.

Tested (run the relevant ones):

• Code formatting: bash format.sh
• Any manual or new tests for this PR (please specify below)
  • AWS launch with tags which which include values of false and true set in the ~/.sky/config.yaml aws.instance_tags section
• All smoke tests: pytest tests/test_smoke.py
• Relevant individual smoke tests: pytest tests/test_smoke.py::test_fill_in_the_name
• Backward compatibility tests: bash tests/backward_comaptibility_tests.sh

[Michaelvll]

Thanks for fixing this @JGSweets! Just tested with the following ~/.sky/config.yaml in master and got the following error, which is fixed in this PR.

aws:
  instance_tags:
    mykey1: "1"
    mykey2: "true"
    mykey3: "hello"
gcp:
  instance_tags:
    mykey1: "1"
    mykey2: "true"
    mykey3: "hello"

D 04-26 20:46:24 provisioner.py:183] botocore.exceptions.ParamValidationError: Parameter validation failed:
D 04-26 20:46:24 provisioner.py:183] Invalid type for parameter TagSpecifications[0].Tags[4].Value, value: 1, type: <class 'int'>, valid types: <class 'str'>
D 04-26 20:46:24 provisioner.py:183] Invalid type for parameter TagSpecifications[0].Tags[5].Value, value: True, type: <class 'bool'>, valid types: <class 'str'>