Force-load Test Dependencies

[ZachNewbery]

Why:

Closes #29

What's being changed (if available, include any code snippets, screenshots, or gifs):

Tests load ctbllib and digraphs to pass when the OnlyNeeded option is used to load the typeset package. Furthermore, as this option may also mean that the initial load of typeset (i.e. when a user loads the package with OnlyNeeded prior to running the test suite) , the RereadPackage option was used in lieu of a simple LoadPackage as digraphs functionality is skipped if the digraphs package is not marked for loading on the initial load.

This commit was tested both using the GAP console (gap -A) with LoadPackage("typeset":OnlyNeeded); TestPackage("typeset":OnlyNeeded), as well as using the test files directly gap testall.g to ensure compliance.

Check off the following:

• I have added the necessary functions to implement my fix in a structured, readable way.
• I have documented my added code to the codebase, added new directories to makedoc.g and new chapters/sections to order_info.g.
• I have tested my additions, and included the tests within the tst directory.
• I have summarised any large features as bullet points in CHANGELOG.md.

[codecov]

Codecov Report

Merging #30 (4b738ec) into main (2ae56a9) will increase coverage by 0.83%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #30      +/-   ##
==========================================
+ Coverage   87.02%   87.86%   +0.83%     
==========================================
  Files          12       12              
  Lines         848      890      +42     
==========================================
+ Hits          738      782      +44     
+ Misses        110      108       -2     

see 6 files with indirect coverage changes

[fingolfin]

Just a quick note: I only saw this PR by pure chance. I get dozens and sometimes hundreds of GitHub notifications every day, and miss many things. I recommend dropping me a quick email if you'd like me to review something.