web stream_color: Test `get_stream_privacy_icon_color`/`get_recipient_bar_color` against a table

[chrisbobbe]

From discussion: https://chat.zulip.org/#narrow/stream/101-design/topic/UI.20redesign.3A.20recipient.20bar.20colors/near/1673209

We should add regression tests for these functions in web/src/stream_color.js:

• get_stream_privacy_icon_color
• get_recipient_bar_color

To do that, let's first make a list of "base" stream colors to test as inputs, including:

• all of the options in the color picker (the stream_color_palette list)
• a variety of custom colors that users can choose (including very light and very dark ones to exercise logic about restricting lightness in the outputs)

Then call the functions on each of those and make a table, like:

Base stream color	get_recipient_bar_color	get_stream_privacy_icon_color
#94c849	#e4eed3	#94c849
#fae589	#f0ead6	#cbb85e
(etc., many more)

We'll hard-code that table in a test file. For the actual tests, we'll go through the table row by row and check that get_stream_privacy_icon_color and get_recipient_bar_color give values that match the table.

The tests should cover both light and dark mode.

[zulipbot]

Hello @zulip/design members, this issue was labeled with the "design", "redesign" labels, so you may want to check it out!

[chrisbobbe]

If the implementation doesn't match the intended design (which is an open question), we should fix the implementation too.