feat: add occupied slots to game rooms api (#641)

[reinaldooli]

This PR implements the changes necessary for Maestro to manage multiple matches per Game Server (pod).

Motivation

Improved Server Utilization: Previously, Maestro treated Game Servers as a single unity of allocation, which was inefficient for games capable of running multiple matches concurrently, as they must implement their own logic to properly send to Maestro the Game Server state (occupied and ready).

Flexible Scaling: By introducing slot-based management, Maestro can better match server scaling to the actual workload, reducing the over-provisioning and improving cost efficiency.

Backward Compatibility: These changes ensure that existing configurations remain unaffected (e.g., default MaxMatches=1), allowing game teams to adopt the new functionality at their own pace.

Key Changes

Scheduler Configuration

• Added the MatchAllocation block with one parameter:
  • MaxMatches: Defines the maximum number of matches a Game Server can handle;

New gameServer State:

• Active: Servers hosting matches but not at full capacity.

Logic Updates

• Autoscaling calculations now account for the number of occupied slots, ensuring more precise scaling decisions;
• Active state is managed only for Scheduler with MaxMatches > 1

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 45.64184% with 343 lines in your changes missing coverage. Please review.

Project coverage is 62.02%. Comparing base (bb118c8) to head (7b1f7db).
Report is 26 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/api/v1/messages.pb.go	31.03%	137 Missing and 3 partials ⚠️
pkg/api/v1/schedulers.pb.go	41.37%	51 Missing ⚠️
pkg/api/v1/rooms.pb.go	35.71%	36 Missing ⚠️
pkg/api/v1/schedulers_grpc.pb.go	0.00%	21 Missing ⚠️
pkg/api/v1/operations.pb.go	23.07%	20 Missing ⚠️
pkg/api/v1/rooms_grpc.pb.go	0.00%	13 Missing ⚠️
internal/core/services/rooms/status.go	60.71%	7 Missing and 4 partials ⚠️
pkg/api/v1/rooms.pb.gw.go	0.00%	8 Missing and 3 partials ⚠️
pkg/api/v1/schedulers.pb.gw.go	9.09%	7 Missing and 3 partials ⚠️
pkg/api/v1/operations_grpc.pb.go	0.00%	9 Missing ⚠️
... and 9 more

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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #651      +/-   ##
==========================================
- Coverage   64.30%   62.02%   -2.28%     
==========================================
  Files          39      141     +102     
  Lines        2905    12111    +9206     
==========================================
+ Hits         1868     7512    +5644     
- Misses        909     4281    +3372     
- Partials      128      318     +190     

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