[Do Not Merge][LibOverhaul 03] Update JsonCpp

[MartinBriza]

📒 Description

To state the obvious, JsonCpp is a third party library we're using to parse Json in the library.
We were using quite an outdated version so I updated it to the latest release (1.9.1).
This also means we had to change the way we're using the library (the classes we used to use are now deprecated) so I added a helper class so we don't have to put in a lot of boilerplate code.

🕶️ Types of changes

• New feature (non-breaking change which adds functionality)

🤯 List of changes

• JsonCpp dependency has been updated

Closes #4463

🔎 Review hints

• Same as with most library overhaul PRs, warnings should disappear and the app should continue to compile and work the same on all platforms.

[NghiaTranUIT]

Basically, this PR works well on all platforms. I double-checked all primary features and it's as we expected.

However, I encountered the crash when trying logging out. The log is pointing to JSON Parser. Therefore, I suppose we should take a look at it.

How to reproduce

1. Check out this PR, and login
2. Start any TE and wait 10s
3. Stop and quickly log-out
4. The crash happens 💥

• Full stack trace: https://pastebin.com/tyLcKQpQ
• Current thread stack trace: https://pastebin.com/SBHR6ryq

Screenshots

[NghiaTranUIT]

Please investigate ☝️ issues

[MartinBriza]

I spent a good while testing this today and it crashes on random locations. I'm starting to suspect I discovered another race condition in the library....