[`InstructBlip`] Add accelerate support for instructblip
# What does this PR do?

As per title, let's make users benefit from 8bit / 4bit loading of instructblip models

cc @amyeroberts @sgugger @NielsRogge 

all `accelerate` tests pass for this model

As a side note, as instruct blip relies on flan-t5 as backbone for some models, therefore it is important to add
```python
_keep_in_fp32_modules = ["wo"]
```
To ensure inference stability in fp16 / int8 / fp4 
_The documentation is not available anymore as the PR was closed or merged._<|||||>Thank you :) could you add an integration test?<|||||>Hey @NielsRogge !
Let's maybe add it together with: https://github.com/huggingface/transformers/pull/24490/files#r1242095062 so we should probably  merge this first :D