adds gradient accumulation to distillation training via tunix

[entrpn]

Description

FIXES b/490478748 which enables gradient accumulation to the distillation training script.

Tests

Ran distillation_checkpointing_test and train_distill_test.

Checklist

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[codecov]

Codecov Report

❌ Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
.../trainers/post_train/distillation/train_distill.py	0.00%	4 Missing ⚠️

📢 Thoughts on this report? Let us know!

[vlad-karp]

LGTM

[richjames0]

lgtm

[gagika]

should this also be updated if gradient_accumulation_steps > 1?

total_opt_steps = student_config.steps // student_config.gradient_accumulation_steps
optimizer = get_distillation_optimizer(student_config, total_opt_steps)