Mwalib

* Modified rf_input.vcs_order to return `input` if `input` is > 255

* Removed dependence on clap 3 via cbindgen

* Updated min rust version to 1.60
* Updated linux tests CI to test on Ubuntu 20.04 and 22.04

* MWAX Voltage Buffer mode `MWAX_BUFFER` is now supported.

* FFI/C: `MetafitsMetadata`->`ra_phase_center_deg` is now NaN not 0 when missing from metafits file.
* FFI/C: `MetafitsMetadata`->`dec_phase_center_deg` is now NaN not 0 when missing from metafits file.
* `MetafitsContext::grid_name` defaults to 'NOGRID' when key is missing from metafits file.
* `MetafitsContext::grid_number` defaults to 0 when key is missing from metafits file.
* `MetafitsContext::sun_alt_deg` is now an Option<f64> to handle cases where key is missing from metafits file. Via FFI/C it is represented by a NaN.
* `MetafitsContext::sun_distance_deg` is now an Option<f64> to handle cases where key is missing from metafits file. Via FFI/C it is represented by a NaN.
* `MetafitsContext::moon_distance_deg` is now an Option<f64> to handle cases where key is missing from metafits file. Via FFI/C it is represented by a NaN.
* `MetafitsContext::jupiter_distance_deg` is now an Option<f64> to handle cases where key is missing from metafits file. Via FFI/C it is represented by a NaN.
* Update module docs.
* Update dependencies.
* Fixed a bunch of clippy lints.

* mwalib now requires Rust version 1.57 or newer
* Speed up conversion of legacy -> MWAX visibility ordering
* Expose all mwalib error types