Improved MissionRole Switch Cases & Role List

[IllianiCBT]

Problem

Currently there are a number of unused roles listed as viable cases in megamek/src/megamek/client/ratgenerator/MissionRole.java.

There are also missing or incorrect roles listed in megamek/docs/RAT Stuff/rat-generator.txt.

Solutions

MissionRole.java

I have gone through and removed any unused cases.

rat-generator.txt

I have clarified that either infantry_support or inf_support are accepted cases for the infantry support role. Both are in use and, while it might be advantageous to unify everything to use the same case, that is beyond the scope of this PR.

I have replaced 'incindiary' with 'incendiary' as the suggested case for units that can set fires. In #5288 Nick suggested we leave uses of 'incindiary' intact, however replacement in this instance leaves other uses intact while ensuring that future uses of the case are using the correct spelling. As this is user facing, I also wanted to ensure that the spelling was correct.

I have added the missing mechanized_ba role and assigned it the definition eligible to be carried by Omni units as mechanized BA.

I changed pocket ws to pocket_warship, as while pocket ws would have been accepted, its only use is in rat-generator.txt so by changing it to pocket_warship I was able to remove that case from MissionRole.java.

Note

This initially started out as an attempt to investigate #5267. However, upon investigation, I found that existing functions relied upon the cases (when used) as currently implemented. As I was unable to find which functions were reliant on the current role cases, I opted instead to just leave the class intact and to only tidy things up so that we weren't checking for unused cases.

[Sleet01]

Looks good to me.