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

Differential Revision: D93186334

[meta-codesync]

@Balandat has exported this pull request. If you are a Meta employee, you can view the originating Diff in D93186334.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 97.50000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 96.78%. Comparing base (d8a75c0) to head (83f550a).

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

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4907      +/-   ##
==========================================
- Coverage   96.78%   96.78%   -0.01%     
==========================================
  Files         593      593              
  Lines       62284    62289       +5     
==========================================
+ Hits        60282    60286       +4     
- Misses       2002     2003       +1     

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