We currently enable the OSC 52 clipboard provider by setting g:clipboard
when a list of conditions are met, one of which is that $SSH_TTY must be
set. We include this condition because often OSC 52 is not the best
clipboard provider, so if there are "local" providers available Nvim
should prefer those over OSC 52.

However, if no other providers are available, Nvim should use OSC 52
even when $SSH_TTY is not set. When a user is in an SSH session then the
checks for the other clipboard providers will still (typically) fail, so
OSC 52 continues to be enabled by default in SSH sessions.

This is marked as a breaking change because there are some cases where
OSC 52 wasn't enabled before and is now (or vice versa).

Problem:
tmux clipboard not used when tmux is a daemon and $TMUX is empty.

Solution:
If `tmux list-buffers` succeeds, use tmux clipboard.

Setting `vim.g.clipboard = false` will use the builtin clipboard
providers.

Closes https://github.com/neovim/neovim/issues/27698.

Co-authored-by: Gregory Anders <greg@gpanders.com>

The benefit of this is that users only pay for what they use. If e.g.
only `vim.lsp.buf_get_clients()` is called then they don't need to load
all modules under `vim.lsp` which could lead to significant startuptime
saving.

Also `vim.lsp.module` is a bit nicer to user compared to
`require("vim.lsp.module")`.

This isn't used for some nested modules such as `filetype` as it breaks
tests with error messages such as "attempt to index field 'detect'".
It's not entirely certain the reason for this, but it is likely it is
due to filetype being precompiled which would imply deferred loading
isn't needed for performance reasons.

Fix #25466