Add symbol and builtin autocompletion

[ferranbt]

No description provided.

[codspeed-hq]

Merging this PR will not alter performance

✅ 74 untouched benchmarks

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_{Comparing feat-autocompletion (1523a16) with hover-func-decl-references (dc0c9bd)¹}

Footnotes

1. No successful run was found on hover-func-decl-references (6323f4b) during the generation of this report, so 9393bd6 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩