fix(tests): fix broken tests on nightly

[fannheyward]

• [x] src/__tests__/snippets/snippet.test.ts #4807, looks like nvim 0.10 changed something will move cursor after snippet session. Use the defaultRange as workaround to make nested tests work.
• [x] src/__tests__/list/mappings.test.ts, xclip doesn't work as expected with nvim 0.10, setup g:clipboard with a fake clipboard function to do testing https://neovim.io/doc/user/provider.html#provider-clipboard
• [x] src/__tests__/handler/highlights.test.ts

Another issue: stable nvim failed with Node 20 runner.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 98.58%. Comparing base (bb6df56) to head (27407fe).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #4901 +/- ## ======================================= Coverage 98.58% 98.58% ======================================= Files 273 273 Lines 26075 26075 Branches 5391 5391 ======================================= + Hits 25705 25706 +1 + Misses 216 215 -1 Partials 154 154 ```

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