Arm backend: Add FuseEqualPlaceholdersPass

[AdrianLundell]

This pass optimizes memory usage by finding constant placeholders pointing to identical tensors and fusing them to one single placeholder with multiple users.

Note that Ethos-U Vela is updated to include a bug fix related to shared buffers.

cc @digantdesai @freddan80 @per @zingo @oscarandersson8218

[pytorch-bot[bot]]

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:white_check_mark: No Failures

As of commit 17455b42e486187856725ae4bdfc9722f4368206 with merge base a4be2e4e26284306e03c4b716317eb0fdf8eac09 (): :green_heart: Looks good so far! There are no failures yet. :green_heart:

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[zingo]

qnn fails are unrelated

[zingo]

@digantdesai How did it go with this? Did you find any problems we should address/fix?

[AdrianLundell]

@digantdesai Hi, is it ok to merge this?

[facebook-github-bot]

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[digantdesai]

Apologies for a delayed response.

Yeah I won't be able to update vela until next week, I pulled this in and if there are no internal failures i.e. the new version of vela is backwards compatible with the one we have internally, we can merge this ASAP.