feat: interactive scaffolding for picking default monitor config

[vigneshshanmugam]

• fix https://github.com/elastic/synthetics-dev/issues/119
• part of Push command final touchup before release  #513
• init command scaffolding asks interactive questions for both Locations and Schedule which would be set as default on the Synthetics.config.ts file to be used when pushing the monitors.
• Error out when push command is invoked without passing the journey file paths
• Make the location and schedule option as required --locations <> in the CLI and error out when not set.
• Allow users to configure the default values via synthetics.config.ts file

How to test

1. Build the agent npm run build
2. Run node dist/cli.js init test-directory
3. Verify if it sets up all the default schedule and locations in the synthetics.config.ts generated file.

[apmmachine]

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• Start Time: 2022-06-02T23:47:00.019+0000

• Duration: 14 min 1 sec

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Test	Results
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Passed	164
Skipped	2
Total	166

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[andrewvc]

LGTM