When PostgreSQL starts, we see the following errors in the logs:
```
mkdir:
cannot create directory ‘/tmp/appsmith/postgres-stats’
: Permission denied
```
And then this over and over again:
```
postgres stdout | 2023-09-19 15:34:34.504 UTC [1759] LOG: could not open temporary statistics file "/tmp/appsmith/postgres-stats/global.tmp": No such file or directory
```
The problem is that in `postgres.conf`, we set `user=postgres`, which
doesn't have access to create things in `/tmp`.
This PR removes this configuration and lets the default be, which will
be a temp folders _under_ the data directory.
This is part of supporting running Appsmith with readonly root FS. This
moves the supervisord configuration, and runtime files, like the unix
socket file, and the PID file, to `$TMP`.
This is another step towards supporting running with readonly root FS,
and only making runtime changes in the container in `/tmp` or in
`/appsmith-stacks`, and nowhere else.
Move the files that are copied into the Docker image, into an `fs`
folder, that reflects the folder structure of that in the image. This
means two things right away:
1. A single `COPY` instruction in `Dockerfile` is enough to copy all the
files to their places.
2. The structure of files in the repo reflects that in the Docker image.
This makes working with the files/folders and troubleshooting with them
much easier.
❗ Note: **There's actually only 3 files changed, rest are just moved.**
