Consolidate the number of .env files that store the same values

[SimiHunjan]

Problem

There are a few locations where the following values are repeated:

# Postgres database
# service name for postgres service in docker
POSTGRES_HOST=database
POSTGRES_PORT=5432
POSTGRES_DATABASE=postgres
POSTGRES_USERNAME=postgres
POSTGRES_PASSWORD=postgres
# should be false in production
POSTGRES_SYNCHRONIZE=true

# PG Admin settings
[email protected]
PGADMIN_DEFAULT_PASSWORD=pgadmin4

NODE_ENV=development

API: https://github.com/hashgraph/hedera-transaction-tool/blob/main/back-end/apps/api/.env.test
Chain: https://github.com/hashgraph/hedera-transaction-tool/blob/main/back-end/apps/chain/example.env
Notifications: https://github.com/hashgraph/hedera-transaction-tool/blob/main/back-end/apps/notifications/example.env
backend Root: https://github.com/hashgraph/hedera-transaction-tool/blob/main/back-end/example.env


### Solution

It seems it would make sense to house these values in one location to call from vs. in multiple locations. 

### Alternatives

_No response_

[SimiHunjan]

It is not important for now but logging this to review in the future.

[RAMTO]

@SimiHunjan Using microservices for the BE requires using different .env files and some of the variables could be duplicated. As discussed with @SvetBorislavov it will be very difficult to consolidate these variables.