Add single-soldier coin training addon

[DevOpsOfChaos]

Summary

• add an optional SINGLE_SOLDIER_COIN_TRAINING addon
• make one gold coin promote only one eligible soldier when the addon is enabled
• select the currently lowest-ranked promotable soldier for that single promotion
• keep the default rank-chain coin training behavior unchanged when the addon is disabled
• add regression coverage for both default chain training and single-soldier training

Motivation

By default, one consumed gold coin can promote a chain of eligible soldiers in a military building. This can make coin usage much more efficient when several promotable soldiers are present, but it also encourages micromanagement when players want to control coin efficiency more narrowly.

This addon provides an optional alternative where each delivered coin promotes only one eligible soldier. The selected soldier is the lowest-rank soldier that can still be promoted, matching the narrow behavior discussed in #1418.

The goal is not to replace the existing training model. It is a small optional gameplay variant for players who prefer one-coin-one-promotion behavior.

Scope / safety notes

This PR only changes how many soldiers one consumed coin can promote when the addon is enabled.

It intentionally does not change:

• gold delivery
• coin storage
• military building capacity
• training timing
• soldier rank limits
• mine output
• default chain-training behavior

When the addon is disabled, the existing promotion-chain behavior remains unchanged.

Validation

• Built Test_integration locally with Visual Studio 2022 / Debug
• Ran Test_integration.exe --run_test=AttackSuite/CoinTrainingUpgradesRankChainByDefault --report_level=short
• Ran Test_integration.exe --run_test=AttackSuite/SingleSoldierCoinTrainingUpgradesOnlyLowestRankSoldier --report_level=short
• Ran Test_integration.exe --run_test=AttackSuite --report_level=short --log_level=error
• Passed locally:
  • 23 test cases out of 190 passed
  • 167 test cases out of 190 skipped
  • 1258 assertions out of 1258 passed

Fixes #1418

[DevOpsOfChaos]

Pushed a small follow-up.

This fixes the formatting issue and moves the addon ID into my own addon namespace as 0x01100002.

No gameplay behavior change.

[DevOpsOfChaos]

Updated the branch against current master and resolved the resulting conflicts.

During the update, the previous addon ID conflicted with the still-open stranded-soldier return-search PR. SINGLE_SOLDIER_COIN_TRAINING now uses the audited free ID 0x01100002; gameplay behavior is unchanged.

Validation passed locally:

• AttackSuite: 24 test cases / 1294 assertions
• default coin-training behavior: 36 assertions
• single-soldier coin-training behavior: 36 assertions
• ctest -R "^Test_integration$": passed
• clang-format dry-run: clean
• git diff --check upstream/master...HEAD: clean

[Flamefire]

Rebased, resolved conflicts and added the remaining change to the test