fix(server): fix the scheduler and the scheduler selection logic

[Tsukilc]

Replaces #2937 so the source branch is hugegraph/hugegraph:fix/scheduler and org collaborators can push follow-up fixes directly.

New Features

Server IDs now support automatic generation, eliminating the need for manual configuration.

Refactoring

Significantly simplified the task scheduling architecture by adopting a single-node scheduling path by default, removing multi-node scheduling and role-election–related controls.

Streamlined server information and scheduling management logic by eliminating redundant multi-node–related workflows.

Configuration Changes

Removed explicit scheduling type configuration; the scheduling mode is now determined by the runtime environment.

Bug Fixes

Adjusted the handling logic for task cancellation/deletion and missing tasks, improving exception handling and state management.

Tests

Updated test cases to accommodate the new scheduling behavior and serialization differences.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 122 lines in your changes missing coverage. Please review.
✅ Project coverage is 1.48%. Comparing base (03e6b8e) to head (abb09aa).

Files with missing lines	Patch %	Lines
...pache/hugegraph/task/DistributedTaskScheduler.java	0.00%	47 Missing ⚠️
...n/java/org/apache/hugegraph/core/GraphManager.java	0.00%	31 Missing ⚠️
...g/apache/hugegraph/task/StandardTaskScheduler.java	0.00%	15 Missing ⚠️
.../apache/hugegraph/task/TaskAndResultScheduler.java	0.00%	14 Missing ⚠️
...n/java/org/apache/hugegraph/StandardHugeGraph.java	0.00%	7 Missing ⚠️
...a/org/apache/hugegraph/task/ServerInfoManager.java	0.00%	5 Missing ⚠️
.../main/java/org/apache/hugegraph/task/HugeTask.java	0.00%	3 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (03e6b8e) and HEAD (abb09aa). Click for more details.

HEAD has 2 uploads less than BASE

Flag	BASE (03e6b8e)	HEAD (abb09aa)
	3	1

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #3082       +/-   ##
============================================
- Coverage     36.80%   1.48%   -35.32%     
+ Complexity      338      21      -317     
============================================
  Files           805     783       -22     
  Lines         68587   65796     -2791     
  Branches       9029    8528      -501     
============================================
- Hits          25241     975    -24266     
- Misses        40653   64737    +24084     
+ Partials       2693      84     -2609     

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