Decrease MSRV to 1.75.0

[EricLBuehler]

Refs NixOS/nixpkgs#319008, decreases MSRV to 1.75.0. Removes AVIF support but this is an OK cost.

[github-actions]

Code Metrics Report

  ===============================================================================
 Language            Files        Lines         Code     Comments       Blanks
===============================================================================
 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
-------------------------------------------------------------------------------
 Jupyter Notebooks       1            0            0            0            0
 |- Markdown             1           60           30           22            8
 |- Python               1           96           87            1            8
 (Total)                            156          117           23           16
-------------------------------------------------------------------------------
 Markdown               19         1371            0         1026          345
 |- BASH                 5          101           98            0            3
 |- Python               5           98           88            0           10
 |- Rust                 3          151          135            6           10
 (Total)                           1721          321         1032          368
-------------------------------------------------------------------------------
 Rust                  122        38402        34740          694         2968
 |- Markdown            59          669           13          618           38
 (Total)                          39071        34753         1312         3006
===============================================================================
 Total                 202        41970        36633         1758         3579
===============================================================================