Drop PyTorch 1.9 support

[carmocca]

Proposed refactor

See title

Motivation

PyTorch 1.13 is released today Oct 27 (at least that's the plan). We already support it and test it.

Pitch

To follow our previous support window of 4 versions, drop 1.9 with PL 1.8

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If you enjoy Lightning, check out our other projects! ⚡

• Metrics: Machine learning metrics for distributed, scalable PyTorch applications.

• Lite: enables pure PyTorch users to scale their existing code on any kind of device while retaining full control over their own loops and optimization logic.

• Flash: The fastest way to get a Lightning baseline! A collection of tasks for fast prototyping, baselining, fine-tuning, and solving problems with deep learning.

• Bolts: Pretrained SOTA Deep Learning models, callbacks, and more for research and production with PyTorch Lightning and PyTorch.

• Lightning Transformers: Flexible interface for high-performance research using SOTA Transformers leveraging PyTorch Lightning, Transformers, and Hydra.

cc @carmocca @akihironitta @borda @justusschock @awaelchli @rohitgr7

[Borda]

let's proceed with this one after #15128 and #15403