Add DeprecationError exception and migrate raise DeprecationWarning usages

[saitcakmak]

Summary:
Introduce DeprecationError(AxError) in ax/exceptions/core.py for hard-break deprecations where accessing a removed/deprecated API should fail immediately with an actionable message.

raise DeprecationWarning(...) is semantically incorrect: DeprecationWarning is a warning category, not an exception type. Raising it (a) does not interoperate with warnings.catch_warnings() / simplefilter("ignore", DeprecationWarning) -- it still crashes -- and (b) violates the Ax team rule that runtime errors should be raised from ax/exceptions types. This diff adds a dedicated error class for that purpose and migrates the existing in-repo raise DeprecationWarning sites to it:

• ax/service/utils/scheduler_options.py (SchedulerOptions)
• ax/adapter/pairwise.py (PairwiseAdapter)
• ax/core/batch_trial.py (_status_quo_weight_override)
• ax/fb/service/ax_batch_client.py (attach_batch_trial)

For soft deprecations that should still work with a notice, continue to use warnings.warn(..., DeprecationWarning) -- this error is only for hard breaks.

This is a prerequisite for migrating RangeParameter.digits (in a stacked diff) off raise DeprecationWarning.

Differential Revision: D107660126

[meta-codesync]

@saitcakmak has exported this pull request. If you are a Meta employee, you can view the originating Diff in D107660126.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 28.57143% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 96.55%. Comparing base (873933b) to head (7001050).

Files with missing lines	Patch %	Lines
ax/adapter/pairwise.py	0.00%	2 Missing ⚠️
ax/service/utils/scheduler_options.py	0.00%	2 Missing ⚠️
ax/core/batch_trial.py	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5224      +/-   ##
==========================================
- Coverage   96.57%   96.55%   -0.02%     
==========================================
  Files         619      619              
  Lines       70140    70143       +3     
==========================================
- Hits        67735    67729       -6     
- Misses       2405     2414       +9     

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