Implement GPTQ quantization

[EricLBuehler]

This PR adds GPTQ quantization (paper here) support.

Refs: #418, #448.

[github-actions]

Code Metrics Report

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 Language            Files        Lines         Code     Comments       Blanks
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 Dockerfile              1           34           25            0            9
 Happy                   1          442          369            0           73
 JSON                    9           21           21            0            0
 Python                 32         1256         1075           37          144
 TOML                   16          444          403            1           40
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 Jupyter Notebooks       1            0            0            0            0
 |- Markdown             1           60           30           22            8
 |- Python               1           96           87            1            8
 (Total)                            156          117           23           16
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 Markdown               18         1321            0          982          339
 |- BASH                 5          100           97            0            3
 |- Python               6          122          110            0           12
 |- Rust                 3          151          135            6           10
 (Total)                           1694          342          988          364
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 Rust                  119        36639        33095          672         2872
 |- Markdown            59          664           13          614           37
 (Total)                          37303        33108         1286         2909
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 Total                 198        40157        34988         1692         3477
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