improve concurrency in the JavaView

[swissiety]

fix getting javaidentifierfactories from view
closes #827

[codecov]

Codecov Report

Attention: 4 lines in your changes are missing coverage. Please review.

Comparison is base (17ae880) 63.69% compared to head (2c00669) 63.88%.

❗ Current head 2c00669 differs from pull request most recent head 16134a5. Consider uploading reports for the commit 16134a5 to get more accurate results

Files	Patch %	Lines
...src/main/java/sootup/java/core/views/JavaView.java	85.71%	3 Missing and 1 partial ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             develop     #828      +/-   ##
=============================================
+ Coverage      63.69%   63.88%   +0.18%     
- Complexity      3435     3438       +3     
=============================================
  Files            313      313              
  Lines          15159    15136      -23     
  Branches        2568     2568              
=============================================
+ Hits            9656     9669      +13     
+ Misses          4597     4562      -35     
+ Partials         906      905       -1     

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