fix: Correctly extract decision when used with prefix

[DrakaSAN]

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

When using a prefix, the TOC generation was failing since the number detection was failing. Update the number detection to account for the prefix.
The TOC generation was using the filename to create the title, instead, do the same thing as the status listing and open the file to extract the title from inside the ADR.

• What is the current behavior? (You can also link to an open issue here)

TOC generator is using getNumberLength to find where the number is. This function is taking the first part of the name without taking a potential prefix into account, which may mean the function returns part of the prefix instead of the number.

TOC generator is using the filename to generate the title of the ADR.

• What is the new behavior (if this is a feature change)?

Extract the first part of the filename after removing the prefix to extract the number.

Copy ListGenerateBuilder and extract the ADR title.

• Other information:

Functionally tested successfully on a small test project, but lacking examples to ensure it didn't break anything else.
Unit test are currently failing and needs to be updated before merging