Support ensure_installed directly in mason

[Limero]

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• Yes

Is your feature request related to a problem? Please describe.

As a follow-up to #483 which adds the ensure_installed option to mason-lspconfig. It would be great if the same functionality could be added to mason itself. I prefer to set up my lsps manually without the use of lspconfig and would want mason to just automatically install them, nothing else.

Describe the solution you'd like

ensure_installed being an option on mason.nvim without requring the use of mason-lspconfig.nvim.

To support the following:

require("mason").setup {
    ensure_installed = {
      "lua_ls",
      "rust_analyzer",
    },
}

Describe potential alternatives you've considered

No response

Additional context

No response