Phase 3: Add Self type annotations to fluent/clone methods

[Balandat]

Summary:
Add Self type annotation from typing module to methods that return self
or cloned instances of the same class. This enables better type inference
for subclasses and improves IDE support.

Files changed:

• ax/core/base_trial.py - run(), stop(), complete(), mark_*() methods
• ax/core/batch_trial.py - mark_arm_abandoned()
• ax/core/experiment.py - add_tracking_metric(), update_tracking_metric(), etc.
• ax/core/multi_type_experiment.py - add_trial_type(), update_runner(), metric methods
• ax/core/arm.py - clone()
• ax/core/objective.py - clone() on Objective, MultiObjective, ScalarizedObjective
• ax/core/optimization_config.py - clone()
• ax/core/runner.py - clone()
• ax/core/parameter.py - clone() abstract method

Reviewed By: saitcakmak

Differential Revision: D91648885

[codecov-commenter]

Codecov Report

❌ Patch coverage is 97.50000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 96.75%. Comparing base (8812057) to head (1ededc9).

Files with missing lines	Patch %	Lines
ax/core/multi_type_experiment.py	85.71%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4870      +/-   ##
==========================================
- Coverage   96.76%   96.75%   -0.01%     
==========================================
  Files         591      591              
  Lines       61879    61884       +5     
==========================================
+ Hits        59875    59878       +3     
- Misses       2004     2006       +2     

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