Add Spring framework RestTemplate SSRF sinks

[Quiark]

Extension functions currently don't work because of #611

[codecov]

Codecov Report

Merging #618 (6ea0a21) into master (46a30fc) will increase coverage by 0.20%.
The diff coverage is 94.11%.

@@             Coverage Diff              @@
##             master     #618      +/-   ##
============================================
+ Coverage     84.70%   84.90%   +0.20%     
- Complexity     1822     1873      +51     
============================================
  Files           151      154       +3     
  Lines          4942     5036      +94     
  Branches       1095     1124      +29     
============================================
+ Hits           4186     4276      +90     
  Misses          339      339              
- Partials        417      421       +4     

Impacted Files	Coverage Δ	Complexity Δ
...dsecbugs/serial/ObjectDeserializationDetector.java	87.50% <75.00%> (+1.01%)	15.00 <0.00> (+1.00)
...findsecbugs/password/HashUnsafeEqualsDetector.java	96.49% <100.00%> (+0.74%)	24.00 <8.00> (+2.00)
...com/h3xstream/findsecbugs/taintanalysis/Taint.java	79.82% <100.00%> (+0.46%)	146.00 <2.00> (+3.00)
...cbugs/taintanalysis/TaintFrameModelingVisitor.java	79.11% <100.00%> (+0.44%)	142.00 <0.00> (+2.00)
...findsecbugs/wicket/WicketXssComponentDetector.java	97.77% <0.00%> (-0.10%)	14.00% <0.00%> (ø%)
.../com/h3xstream/findsecbugs/xss/XssJspDetector.java	80.00% <0.00%> (ø)	8.00% <0.00%> (ø%)
...m/findsecbugs/ldap/LdapEntryPoisoningDetector.java	92.30% <0.00%> (ø)	10.00% <0.00%> (ø%)
...m/findsecbugs/spring/CorsRegistryCORSDetector.java	82.85% <0.00%> (ø)	9.00% <0.00%> (ø%)
...gs/password/IntuitiveHardcodePasswordDetector.java	94.73% <0.00%> (ø)	10.00% <0.00%> (ø%)
...stream/findsecbugs/groovy/GroovyShellDetector.java	83.33% <0.00%> (ø)	7.00% <0.00%> (?%)
... and 11 more

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[h3xstream]

Looks good! 👌
The only thing missing is at least one test cases.

I see many stub classes but none are used by test cases (not test samples).