feat: Add JSON Lines Support to KV Store

[jshlbrd]

Description

• Adds support for JSON Lines in the JSON File KV store

Motivation and Context

GJSON has native support for JSON Lines and this is the simplest way to support using them as a KV store.

How Has This Been Tested?

Integration tested using the development app. The test can be recreated with these configs:

kv.json

{"a":1}
{"b":2}
{"c":3}
{"d":4}
{"e":5}

process.libsonnet

local sub = import '../../build/config/substation.libsonnet';

local processors = [ { processor: sub.interfaces.processor.kv_store( options={ type: 'get', kv_options: sub.interfaces.kv_store.json_file( settings={file: 'kv.json', is_lines: true} ) }, settings={key: 'bar', set_key: 'kv_store'} ) }, ];

{ processors: sub.helpers.flatten_processors(processors), }

> data.json
```json
{"foo":"a"}
{"bar":"b"}
{"baz":"c"}
{"qux":"d"}
{"quux":"e"}

The results are:

{"foo":"a","kv_store":null}
{"bar":"b","kv_store":2}
{"baz":"c","kv_store":null}
{"qux":"d","kv_store":null}
{"quux":"e","kv_store":null}

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [x] My code follows the code style of this project.
• [x] My change requires a change to the documentation.
• [x] I have updated the documentation accordingly.