[RUM-11388] Fix FileBasedConfiguration related issues

[sbarrio]

What does this PR do?

This PR aims to fix several issues with FileBasedConfiguration initialization of the SDK.

1.- Fixes a reported issue that makes it so directly passing a configuration json file enforces users to duplicate and nest another configuration property for it to work, ignoring the structure defined on datadog-configuration.schema.json. Doing so makes the schema validator label the json configuration as invalid. I fixed it so it properly accepts the schema we enforce with just one configuration entry.

This means that creating a new FileBasedConfiguration can be done like so:

// 1.- File based configuration from .json
const configuration = new FileBasedConfiguration(require("../datadog-configuration.json"));

// 2.- File based configuration from .json and custom mapper setup
const configuration = new FileBasedConfiguration( {
   configuration: require("../datadog-configuration.json").configuration, 
   errorEventMapper: (event) => event, 
   resourceEventMapper: (event) => event, 
   actionEventMapper: (event) => event}
);

2.- Removes the automatic loading of a datadog-configuration.json file by not passing a config file to FileBasedConfiguration(). The way in which this was done was flimsy, as it relied on jumping out of node_modules up to the root app folder. This worked most of the time but it caused an issue generating a require cycle that made 2 of our internal enums to be undefined at runtime (TrackingConsent and SdkVerbosity).

3.- Updates the FileBasedConfiguration tests to be more thorough and cover edge cases properly.

4.- Expands the example app showcasing different ways to provide a configuration object to the DatadogProvider, including FileBasedConfiguration schemes.

Motivation

FileBasedConfiguration should consistently work across the board.

Additional notes

This is a breaking change, as the option of automatically looking for a config.json file without having the user provide a specific path when creating a FileBasedConfiguration object will cease to work.

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests
• Make sure you discussed the feature or bugfix with the maintaining team in an Issue
• Make sure each commit and the PR mention the Issue number (cf the CONTRIBUTING doc)
• If this PR is auto-generated, please make sure also to manually update the code related to the change

[buraizu]

Just flagging some typos and suggesting a few other updates for consistency

[sbarrio]

Just flagging some typos and suggesting a few other updates for consistency

@buraizu Hi, thanks for raising all those typos 🙇

If you don't mind, I'll open a separate PR with your changes, as this specific PR is aimed toward a feature branch, and I think it's better to apply these corrections directly on develop.

EDIT: I've opened a PR with these fixes here.