add activation checkpoint for batch_split

[suexu1025]

Description

• add activation checkpoint for batch split

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[codecov]

Codecov Report

❌ Patch coverage is 66.66667% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/MaxText/layers/deepseek_batchsplit.py	0.00%	1 Missing ⚠️

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[NuojCheng]

LGTM but I suggest adding "attention_out" to other attention modules as well for consistency, e.g. attention_op.py, attention_mla.py.

[suexu1025]

LGTM but I suggest adding "attention_out" to other attention modules as well for consistency, e.g. attention_op.py, attention_mla.py.

just updated, added attention_out for both other attention files to be consistent available config.

[RissyRan]

Shall we reuse context for attention out?