[DRAFT] Fix pooling accum_t autoset & avoid global override

[calad0i]

A# Description

No test at the moment - Fix a series of strange accum_t behaviors for pooling layers in the current version. Potential conflict with #855, would need to converge first before finalizing changes.

Strange behaviors:

• model_default precision overridden
• Extra integer bits were added, while the number of fp bits decreased

Type of change

• [x] Bug fix (non-breaking change that fixes an issue)

Tests

Not yet available.

Test Configuration:

Checklist

• [x] I have read the guidelines for contributing.
• [x] I have commented my code, particularly in hard-to-understand areas.
• [ ] I have made corresponding changes to the documentation.
• [x] My changes generate no new warnings.
• [x] I have installed and run pre-commit on the files I edited or added.
• [ ] I have added tests that prove my fix is effective or that my feature works.