Add option to disable auto detection of indentation style

[bpandreotti]

Currently, when loading a file, the indentation style is detected using a heuristic that can sometimes make mistakes (see #9556, #9822). This PR adds an auto-detect-indent option, which defaults to true, that allows users to change this behaviour. When auto-detect-indent is set to false, instead of trying to detect the indent syle, Helix will just use the ident style defined in the language configuration.

[pascalkuthe]

I don't see us adding this to core. We dont like adding condig options. We should rather improve the indent detection and allow modlines to manually overwrite in the rare edgecases. Thank you for contributing