Fix project settings file getting corrupted

[AliAlbarrak]

Why this change?

This resolve the settings file corruption as described in #524

Even though reading and writing of the settings file is protected by a lock, it is possible (due to domain reload) that 2 separate running processes are trying to access the file at the same time so the lock in one process is not aware of the other process.

A scenario like this could happen.

1. Code in domain A will start writing to ProjectsSettings file
2. Code in domain B will start reading the file
3. If domain A didn't finish writing yet, domain B will encounter unexpected EOF
4. Domain B will assume the file is broken and reset settings
5. Domain B will write default settings to ProjectsSettings file

What did I do?

I made the writing happen to a temporary file. When the writing is complete, copy the temp file to the target path. This avoids the file being in an "invalid state" for a short time during the writing.

Review

Feedback is greatly appreciated and please let me know which steps I need to take to make my change release-ready.

[AliAlbarrak]

As reported here, this fix fails sometimes so I'll draft the pull request until I find a better solution

[AliAlbarrak]

The settings file gets written multiple times with every domain reload/compile, even when settings didn't change. I added an extra check to skip file write if settings didn't change since last read.

[AliAlbarrak]

Hello @a-maurice @chkuang-g and team
I'd appreciate it if you can guide me through what I need to do to get this reviewed and merged. This PR is associated with the top voted 👍 issue #524. I believe it will be great UX improvement for most users to get it fixed.

[Nezz]

We'd love to have this incorporated - this is a very annoying issue.

[cmcpasserby]

really can non one review this and get it merged in? This issue has been going on for years and makes working with this very annoying and tedious

[Tommigun1980]

I tested this pull request and my findings are at #524 (comment)

[TyelorD]

I think this pull looks good to me, aside from the one change I requested.

That said, I'm not affiliated with Google in any way.

[berniegp]

Hi! I still got settings corruption with your version. However I think I found the source of the problem and a fix here #678.

[AliAlbarrak]

I guess this is no longer needed since #678 was merged 🎉