feat: enable sub-64px dimensions

Description

Issue

This is the seventh Merge Request from the SVT-AV1-PSY team aiming to integrate our features into mainline SVT-AV1 under the oversight of Hassene Tmar and Faouzi Kossentini. This MR enables encoding of source media with dimensions smaller than 64x64px.

@hassount mentioned that this limitation was imposed intentionally in the past due to crashes encountered with small dimensions. We had a user report something like this to SVT-AV1-PSY's bug tracker, and I've included the fix in this commit. I'm not sure if this fixes encoding with small dimensions in all cases, but I haven't personally encountered any crashes since this fix was incorporated.

Author(s)

@juliobbv

Performance impact

• quality
• memory
• speed
• 8 bit
• 10 bit
• N/A

Test set

• obj-1-fast can be found here
• other
• N/A

Merge method

• Allow the maintainer to squash and merge when PR is ready to create a 1-commit to the master branch. The maintainer will be able to fix typos / combine commit messages to create a more readable 1-commit message or use whatever is stated in the 'Description' section
• I will clean up my commits and the maintainer shall use 'rebase and merge' to the master branch