feat: telescope preview

[xieyonn]

1. Remove deprecated function vim.api.nvim_buf_add_highlight, add a helper buf builder.
2. Add missing annotation style.
3. Use a global variable _G.__fidget_telescope_config is not a good design, and we do not need either.
4. Remove option use_previewer because set previewer = false in telescope config will just work.

eg:
disable previewer by default, but you can still toggle previewer window.

require("telescope").extensions.fidget.fidget({ previewer = false })

or in telescope extension config.

require("telescope").setup({
  extensions = {
    fidget = {
      previewer = false,
    },
  },
})

before:

after:

[xieyonn]

remove use_preview may break your config.
You can just put wrap_text option in telescope config or via api.

require("telescope").setup({
  extensions = {
    fidget = {
      previewer = false,
      wrap_text = false,
    },
  },
})

cc @ButterSus @lucykowal

[nqrk]

Instead of adding a new file (buf.lua) in core, wouldn't it make sense to group any code related to telescope in the telescope extension directory?