Indentation rework (#1562)

* WIP: Rework indentation system

* Add ComplexNode for context-aware indentation (including a proof of concept for assignment statements in rust)

* Add switch statements to Go indents.toml (fixes the second half of issue #1523)
Remove commented-out code

* Migrate all existing indentation queries.
Add more options to ComplexNode and use them to improve C/C++ indentation.

* Add comments & replace Option<Vec<_>> with Vec<_>

* Add more detailed documentation for tree-sitter indentation

* Improve code style in indent.rs

* Use tree-sitter queries for indentation instead of TOML config.
Migrate existing indent queries.

* Add documentation for the new indent queries.
Change xtask docgen to look for indents.scm instead of indents.toml

* Improve code style in indent.rs.
Fix an issue with the rust indent query.

* Move indentation test sources to separate files.
Add `#not-kind-eq?`, `#same-line?` and `#not-same-line` custom predicates.
Improve the rust and c indent queries.

* Fix indent test.
Improve rust indent queries.

* Move indentation tests to integration test folder.

* Improve code style in indent.rs.
Reuse tree-sitter cursors for indentation queries.

* Migrate HCL indent query

* Replace custom loading in indent tests with a designated languages.toml

* Update indent query file name for --health command.

* Fix single-space formatting in indent queries.

* Add explanation for unwrapping.

Co-authored-by: Triton171 <triton0171@gmail.com>

runtime/queries/cpp/indents.scm

@@ -0,0 +1,3 @@
+; inherits: c
+
+(access_specifier) @outdent