I am currently using neovim nightly and though I am getting InlayHints for rust it is only parameter types I am not getting lifetime ellision hints on trying to change the configuration I saw on the rust_analyzer docs..
I have tried multiple approaches like using setup_handlers of mason-lspconfig.
Trying to setup the lsp outside of the mason-lspconfig.

vim.api.nvim_create_autocmd('LspAttach', {
    group = vim.api.nvim_create_augroup('user_lsp_attach', { clear = true }),
    callback = function(event)
        local opts = { buffer = event.buf }

        vim.keymap.set("n", '<C-i>', function() vim.lsp.inlay_hint.enable(0, not vim.lsp.inlay_hint.is_enabled(0)) end,
            opts)
    end,
})


local lsp_capabilities = require('cmp_nvim_lsp').default_capabilities()

require('mason').setup({})
require('mason-lspconfig').setup({
    ensure_installed = { 'tsserver', 'rust_analyzer', 'clangd' },
    handlers = {
        function(server_name)
            require('lspconfig')[server_name].setup({
                capabilities = lsp_capabilities,
            })
        end,
        rust_analyzer = function()
            require('lspconfig').rust_analyzer.setup({
                capabilities = lsp_capabilities,
                settings = {
                    ['rust_analyzer'] = {
                        inlayHints = {
                                lifetimeElisionHints = {
                                    enable = "always",
                                    useParameterNames = true
                                }

                        },
                    }
                }
            })
        end
   }
})