refactor!: migrate to mason.nvim

[kylo252]

Description

mason.nvim is the next generation version of nvim-lsp-installer. It builds on
top of the very same foundation as nvim-lsp-installer, but with a majority of
internals refactored to improve extensibility and testability.

fixes #2850

TODOs

• replace nvim-lsp-installer completely
• ensure that template generation still works
• fix data-race on server install (on_server_ready has been removed..)
• make sure no deprecated/outdated commands exist (how to replace LspInstallInfo?)
• add null-ls integration (requires a separate PR)
• add DAP integration (requires a separate PR)

[ghost]

This completely broke my rust-tools configuration which is 1:1 from https://www.lunarvim.org/languages/rust.html#extra-plugins.

Are those random breaking changes supposed to happen in rolling? Then a more suited branch name would be 'unstable' instead.

[kylo252]

This completely broke my rust-tools configuration which is 1:1 from https://www.lunarvim.org/languages/rust.html#extra-plugins.

just remove all references to lsp-installer and it should work.

Are those random breaking changes supposed to happen in rolling? Then a more suited branch name would be 'unstable' instead.

there's a reason why the master branch exists along with its version releases.