Add the ci_job_inputs table

What does this MR do and why?

This MR adds a new ci_job_inputs table. This table will support the new job inputs feature. For each input defined in a CI job's configuration, it stores the input name, encrypted input value, and the type of the input. It also stores whether the input is sensitive or not. Sensitive inputs will not be revealed in job logs.

Epic: CI Job Inputs (&17833 - closed)

Issue: Add database table for CI job inputs (#547439 - closed)

Changelog: added

Items postponed to follow-ups:

• Adding a JSON schema validation for the structure of value - Add JSON schema validation to value field on ci... (#554208 - closed)
• Limiting inputs to 20 per job - Limit job inputs to 20 per build (#554211 - closed)
• Adding the enum values for input_type - Fill out enum for ci_job_inputs input_type field (#554212 - closed)
• Clone inputs for Ci::Build - Clone job inputs in the Build model (#554204 - closed)