Realize generic navigation structure

[Drodt]

Related Issue

This pull request depends on #3436.

Intended Change

Previously, the SyntaxElement interface was introduced with the intent of a common supertype and navigation structure for generic AST elements. This PR adds functionality for navigation through ASTs. It serves as a ground for a rewrite of AST visitors, walkers, and matching; each of which will have their separate PR.

Type of pull request

• Refactoring (behaviour should not change or only minimally change)
• New feature (non-breaking change which adds functionality)
• There are changes to the (Java) code

Ensuring quality

• I made sure that the introduced/changed code is well documented (Javadoc and inline comments).
• I have tested the feature as follows: automatic tests

Additional information and contact(s)

The contributions within this pull request are licensed under GPLv2 (only) for inclusion in KeY.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 43.03030% with 94 lines in your changes missing coverage. Please review.

Project coverage is 38.04%. Comparing base (1b48b9e) to head (a4de274). Report is 92 commits behind head on main.

Files	Patch %	Lines
...core/src/main/java/org/key_project/logic/Term.java	0.00%	11 Missing :warning:
...src/main/java/de/uka/ilkd/key/logic/JavaBlock.java	0.00%	6 Missing :warning:
.../uka/ilkd/key/speclang/DependencyContractImpl.java	0.00%	6 Missing :warning:
...c/main/java/org/key_project/logic/op/Modality.java	0.00%	6 Missing :warning:
...e/uka/ilkd/key/logic/op/SortDependingFunction.java	28.57%	5 Missing :warning:
...ava/de/uka/ilkd/key/logic/op/ElementaryUpdate.java	0.00%	4 Missing :warning:
...ava/de/uka/ilkd/key/logic/op/ObserverFunction.java	33.33%	4 Missing :warning:
...src/main/java/de/uka/ilkd/key/pp/LogicPrinter.java	0.00%	3 Missing and 1 partial :warning:
...ava/org/key_project/logic/SyntaxElementCursor.java	89.74%	4 Missing :warning:
...java/de/uka/ilkd/key/logic/op/ProgramVariable.java	0.00%	3 Missing :warning:
... and 25 more

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #3472 +/- ## ============================================ + Coverage 38.03% 38.04% +0.01% - Complexity 17089 17117 +28 ============================================ Files 2099 2105 +6 Lines 127274 127439 +165 Branches 21386 21401 +15 ============================================ + Hits 48409 48487 +78 - Misses 72892 72978 +86 - Partials 5973 5974 +1 ```

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[tobias-rnh]

Can you add functionality to the SyntaxElementCursor to go to the next node in the tree?

[Drodt]

Can you add functionality to the SyntaxElementCursor to go to the next node in the tree?

Done!