This will help manage the overly granular checkhealth completion to go
from

```
vim.health
vim.lsp
vim.provider.clipboard
vim.provider.node
vim.provider.perl
vim.provider.python
vim.provider.ruby
vim.treesitter
```

to

```
vim.health
vim.lsp
vim.provider
vim.treesitter
```

`vim.health` is not a "plugin" but part of our Lua API and the
documentation should reflect that. This also helps make the
documentation maintenance easier as it is now generated.

The namespacing for healthchecks for neovim modules is inconsistent and
confusing. The completion for `:checkhealth` with `--clean` gives

```
nvim
provider.clipboard
provider.node
provider.perl
provider.python
provider.ruby
vim.lsp
vim.treesitter
```

There are now three top-level module names for nvim: `nvim`, `provider`
and `vim` with no signs of stopping. The `nvim` name is especially
confusing as it does not contain all neovim checkhealths, which makes it
almost a decoy healthcheck.

The confusion only worsens if you add plugins to the mix:

```
lazy
mason
nvim
nvim-treesitter
provider.clipboard
provider.node
provider.perl
provider.python
provider.ruby
telescope
vim.lsp
vim.treesitter
```

Another problem with the current approach is that it's not easy to run
nvim-only healthchecks since they don't share the same namespace. The
current approach would be to run `:che nvim vim.* provider.*` and would
also require the user to know these are the neovim modules.

Instead, use this alternative structure:

```
vim.health
vim.lsp
vim.provider.clipboard
vim.provider.node
vim.provider.perl
vim.provider.python
vim.provider.ruby
vim.treesitter
```

and

```
lazy
mason
nvim-treesitter
telescope
vim.health
vim.lsp
vim.provider.clipboard
vim.provider.node
vim.provider.perl
vim.provider.python
vim.provider.ruby
vim.treesitter
```

Now, the entries are properly sorted and running nvim-only healthchecks
requires running only `:che vim.*`.