Refactor Numbers and Conversion clients to use DynamicEndpoint

[SMadani]

This continues the work of moving to a more declarative way of implementing and testing endpoints by decoupling from Apache HttpClient. This PR targets the Numbers and Conversion APIs.

[codecov-commenter]

Codecov Report

Merging #477 (f2abb49) into main (5ee1f52) will decrease coverage by 0.02%.
The diff coverage is 91.86%.

@@             Coverage Diff              @@
##               main     #477      +/-   ##
============================================
- Coverage     93.55%   93.53%   -0.02%     
+ Complexity     2884     2855      -29     
============================================
  Files           443      439       -4     
  Lines          7294     7243      -51     
  Branches        440      443       +3     
============================================
- Hits           6824     6775      -49     
+ Misses          279      275       -4     
- Partials        191      193       +2     

Files Changed	Coverage Δ
...a/com/vonage/client/numbers/ListNumbersFilter.java	93.75% <77.77%> (-6.25%)	⬇️
...com/vonage/client/numbers/SearchNumbersFilter.java	92.30% <81.81%> (-4.92%)	⬇️
...a/com/vonage/client/numbers/BaseNumberRequest.java	83.33% <83.33%> (ø)
...onage/client/numbers/NumbersResponseException.java	87.50% <87.50%> (ø)
...com/vonage/client/conversion/ConversionClient.java	100.00% <100.00%> (ø)
...om/vonage/client/conversion/ConversionRequest.java	100.00% <100.00%> (ø)
...va/com/vonage/client/numbers/BuyNumberRequest.java	100.00% <100.00%> (ø)
...com/vonage/client/numbers/CancelNumberRequest.java	100.00% <100.00%> (ø)
...com/vonage/client/numbers/ListNumbersResponse.java	100.00% <100.00%> (ø)
.../java/com/vonage/client/numbers/NumbersClient.java	100.00% <100.00%> (ø)
... and 3 more

... and 1 file with indirect coverage changes

[maxkahan]

I love it, I'll take 100