Implement cache shifting for Llama models

[EricLBuehler]

If this works, we can extend it to the other models.

Hopefully, this will fix the problem in #339 for models without sliding window attention.

[github-actions]

Code Metrics Report

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 Happy                   1          442          369            0           73
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 Python                 21          741          622           21           98
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 Markdown               15         1026            0          758          268
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 Rust                   84        27822        25504          356         1962
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 (Total)                          28241        25504          763         1974
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 Total                 144        30464        26882         1136         2446
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