refactor(linux): conventional Cargo manifests and module files

[datlechin]

Why

The Linux workspace wrote Cargo defaults out by hand, gave every member its own path to each internal crate, named the driver libs drivers_<x> apart from their packages, and used two module layouts.

Change

• Driver libs take their package names (tablepro_driver_<x>). [lib], [[bin]] and [[test]] keys that restate defaults are gone; publish.workspace = true; resolver = "3".
• Internal crates and rustix are declared once in [workspace.dependencies]. Dev-dependencies that repeat a normal one are dropped. Cargo.lock is unchanged.
• One module layout: the seven foo.rs plus foo/ modules become foo/mod.rs, held by clippy::self_named_module_files. ui/export_dialog.rs moves to ui/export/dialog.rs, and three *_tests.rs files become tests submodules.
• meson_options.txt is now meson.options; rustfmt drops the default use_small_heuristics.

Verified

In ubuntu:26.04: fmt check, clippy with and without default features, meson compile and dist, all 7 meson test suites under xvfb, cargo shear, the docs check.