Adding Rope scaling.

[Narsil]

What does this PR do?

• Adds Rope NTK scaling.

Done because #529 was closed
Took some code from huggingface/transformers#24653

• --rope-scaling and --rope-factor are added separately. I considered having a single one and parsing something line ("linear:4.0" , or "dynamic") but decided against
  it because it would push more parsing+validation a bit everywhere (both in the launcher and the server).

Fixes #512

Fixes # (issue)

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[gante]

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