Remove useless steps from Rust CI pipeline

[esteffin]

Removed 3 useless steps from the CBMC Rust:

1. now we build only the required cprover-api-cpp target and its transitive dependencies excluding all binaries not needed, unit tests and JBMC.
2. we add -DWITH_JBMC=OFF to the cmake arguments removing the configuration steps for it.
3. we removed the installation of maven used only when building JBMC that is now not happening.

• Each commit message has a non-empty body, explaining why the change was made.
• Methods or procedures I have added are documented, following the guidelines provided in CODING_STANDARD.md.
• The feature or user visible behaviour I have added or modified has been documented in the User Guide in doc/cprover-manual/
• Regression or unit tests are included, or existing tests cover the modified code (in this case I have detailed which ones those are in the commit message).
• My commit message includes data points confirming performance improvements (if claimed).
• My PR is restricted to a single feature or bugfix.
• White-space or formatting changes outside the feature-related changed lines are in commits of their own.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (ea34799) 79.10% compared to head (fc64f4f) 79.10%.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #8030   +/-   ##
========================================
  Coverage    79.10%   79.10%           
========================================
  Files         1699     1699           
  Lines       196508   196508           
========================================
  Hits        155446   155446           
  Misses       41062    41062           

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