Update and migrate most Realguns content to core

[Rail-Runner]

Summary

SUMMARY: Content "Update and migrate most Realguns content to core"

Purpose of change

Prevent mod content from becoming broken as updates to core game happen (as long as said content is actually reasonable to have in core)

Describe the solution

Move JSON entries from "realguns" folder to appropriate core folders, as well as update them to be more consistent and actually working with current game version.

Had to do some changes to core content as well:

1. Reduced M1911A1 in .38 Super magazine capacity to 9 from 10, seems like it really is 9 rather than 10.
2. Taurus Raging Bull no longer can fire .410 shot ammo; newly added Taurus Raging Judge Magnum does that now.
3. Added .38 6-round speedloader, to go with S&W Model 10 revolver.
4. .454 speedloader can hold .410 shot ammo as well now.

Describe alternatives you've considered

None.

Testing

Copied changes over to game files, made sure that it runs fine, messed around with a couple added guns to make sure that they behave as expected.

Additional context

Any reference for how common the added firearms would be could be useful; I didn't change them from what the mod had.