Database functions fail if db_password contains special characters

[yorkshire-pudding]

This also applies to db_name and db_username but these are less likely to have special characters.
For the purposes of Backdrop where rawurlencode is used, special means anything except A-Z, a-z, 0-1, - _ . ~
https://www.php.net/manual/en/function.rawurlencode.php

Steps to reproduce

1. Create a backdrop database
2. Set the users password to have special characters
3. Attempt install, db-import, db-export, sql, or status --show-password

Expected result works as normal

Actual results
install, db-import, db-export, sql will all fail
status --show-password will show the encoded password

The backdrop GUI installer core/install.php, powered by core/includes/install.inc, uses rawurlencode() for db_name, db_username and db_password so what is stored in settings.php has these values encoded.

If the rawurldecode() function is not used to read the database information stored in settings.php then the value returned will be encoded and so won't match the actual DB password.

[ghost]

Left a review requesting changes.

[yorkshire-pudding]

@BWPanda - done all the db.bee.inc changes.
Might be worth a discussion about the install.bee.inc changes. As stated on the PR, I tried parse_url and it couldn't handle complex passwords.

[ghost]

Thanks so much for this @yorkshire-pudding! Did a final review, made one small change I didn't notice before, and merged!