Add more SRM configs from BDB and general cleanup

[Capkirk123]

Add new SRMs from BDB, including

• Agena Retro Type III
• Agena Spin Rocket
• Alcyone-1 (BE-3)
• M55
• SR19
• SR73
• TX-280 (S-IVB Ullage Motor)
• Star-13/Star-13A

Also clean up BDB assets and add a few missing texture files

Needs https://github.com/KSP-RO/RealismOverhaul/pull/2963

[github-actions[bot]]

Download the artifacts for this pull request:

• ROEngines.zip