This updates the extmark namespace to search for when filtering out
semantic tokens to match the new namespace style recently introduced.

Problem: It is not obvious if a treesitter highlight priority shown in
`:Inspect` is higher or lower than the default.

Solution: Also print default priority (`vim.hl.priorities.treesitter`).
Add padding for better readability.

Problem: `:Inspect` does not show priority for treesitter highlights,
leading to confusion why sometimes earlier highlights override later
highlights.

Solution: Also print priority metadata if set.

An implication of this current approach is that `NVIM_API_LEVEL` should be
bumped when a new Lua function is added.

TODO(future): add a lint check which requires `@since` on all new functions.

ref #25416

This mostly means replacing `nvim_buf_call` and `nvim_win_call` with
`vim._with`.

- Tags are now created with `[tag]()`
- References are now created with `[tag]`
- Code spans are no longer wrapped