Ghost Code for Rust

[Drodt]

Intended Change

Add ghost code. BSc Thesis of Yeseul Park.

Type of pull request

• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• There are changes to the (Java) code
• There are changes to the taclet rule base

Ensuring quality

• I made sure that introduced/changed code is well documented (javadoc and inline comments).
• I made sure that new/changed end-user features are well documented (https://github.com/KeYProject/key-docs).
• I added new test case(s) for new functionality.
• I have tested the feature as follows: ...
• I have checked that runtime performance has not deteriorated.
• For new Gradle modules: I added the Gradle module to the test matrix in
  .github/workflows/tests.yml

Additional information and contact(s)

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