Fix timestamp

[Porges]

Closes #3171.

TimeStamp should be cased Timestamp to match the Python API.

Timestamp was also missing and/or wrong from several of the new response types.

[codecov-commenter]

Codecov Report

Merging #3237 (53498ab) into main (c61aa0a) will increase coverage by 0.30%.
The diff coverage is 40.00%.

@@            Coverage Diff             @@
##             main    #3237      +/-   ##
==========================================
+ Coverage   29.65%   29.95%   +0.30%     
==========================================
  Files         332      301      -31     
  Lines       39290    33662    -5628     
==========================================
- Hits        11651    10084    -1567     
+ Misses      27639    23578    -4061     

Impacted Files	Coverage Δ
src/ApiService/ApiService/Functions/Tasks.cs	19.67% <0.00%> (-0.17%)	⬇️
...piService/ApiService/onefuzzlib/ProxyOperations.cs	0.00% <0.00%> (ø)
src/ApiService/ApiService/onefuzzlib/Scheduler.cs	14.51% <0.00%> (ø)
...rvice/ApiService/onefuzzlib/TaskEventOperations.cs	7.14% <0.00%> (ø)
src/ApiService/Tests/OrmTest.cs	3.88% <0.00%> (ø)
...rc/ApiService/ApiService/OneFuzzTypes/Responses.cs	77.31% <62.50%> (-0.46%)	⬇️
...rvice/ApiService/onefuzzlib/orm/EntityConverter.cs	90.59% <100.00%> (ø)

... and 54 files with indirect coverage changes