Connections: Add Spark option for R and Postgre for Python

[dfalbel]

Adresses: #6186
Adresses: #6184
Addresses: #6188
Addresses: #6453

Adds options for connecting to Spark with R and Postgres with Python.
Also adds icons for connections, so they are nicely rendered in the new connections modal:

I'm not sure though what's the correct way to make sure we have the correct copyright notice.

Also fixes a few bugs:

• Rendering of icons when the backend didn't provide one was broken after Connections: Fix icon rendering on Windows #6370
• The connection string stored after connecting with sqlalchemy didn't include the password.

Release Notes

New Features

• Added Spark and PostgreSQL as options when creating new connections using the Connections Pane.

Bug Fixes

• N/A

QA Notes

Not sure if it's worth testing that generated code is valid for now. Setting up both Spark and Postgre locally can be tricky.

For spark, the following should work:

# Run once
install.packages("sparklyr")
sparklyr::spark_install()

# Connect to Spark local
library(sparklyr)
sc <- spark_connect(master = "local")

For PostgreSQL, it's also not very easy to spin up a local DB for testing. The following worked for me:

brew services start postgresql

Happy to help with the set up :)

CI failures are related to #6496

@:connections

[github-actions]

E2E Tests 🚀
This PR will run tests tagged with: @:critical @:connections

^{readme  valid tags}

[jmcphers]

LGTM!