Make the Big5 unit tests works

[akumria]

The current Big5 unittests are marked as "Incomplete".

The listed reason was that no assertions were made.

The following patches:

• fix some whitespace issues
• load the test data
• test against that data (i.e. does some assertions)

I have also attached an updated big5.txt files:

• the original was *NOT* in Big5
• this is from Wikipedia (​https://en.wikipedia.org/wiki/Big5)
• specifically ​http://ftp.isu.edu.tw/pub/Windows/Chinese/font/chinasea/csw10_exp.txt
• I have removed the majority of that file and reduced the number of strings to 5 (to match the number in tests/phpunit/data/formatting/utf-8/utf-8.txt)

[akumria]

5 Big5 strings

[akumria]

whitespace fix

[akumria]

read in the Big5 data

[akumria]

Test Big5 strings

[boonebgorges]

This looks good, thanks! Looking forward to getting rid of that annoying yellow "I" :)

[boonebgorges]

In 30525:

Repair the seems_utf8() tests that use Big5 encoding.

• Provide sample data that is actually encoded in Big5.
• Do some actual assertions against that data.

Props akumria.
Fixes #30455.