Implement #4397 Internal Bomb Bay (MHQ compatibility)

[Sleet01]

This PR must be taken into MHQ after MegaMek PR #4974 is pulled.

Changes:

• fixes a unit test that fails once AeroSpaceFighter class is introduced.
• Makes clearGameData (called after MM games return to MHQ) aware of Internal and External bomb stores.
• Add handling for internal bombs in XML writer.
• Misc. commenting around bomb panel code explaining changes.

Testing:

• Added, changed, removed bombs from various Aerospace units with and without Internal Bomb Bay quirk.
• Ran all unit tests.

Note: tests for this PR will fail until MegaMek PR #4974 #5003 is pulled.