[FIX] types requiring imports in alloff, conint, confloat

[krezac]

Hi Koudai,
thanks for yopur effort on that project, it's useful for us.
Here are couple of fixes I had to implement to be able to process our swagger file.

• if fields in unnamed object combined with ref in allOf require imports (i.e. string/date), these imports were not included. I'm not sure I've added it the best way, feel free to refactor. AnyOf seems to be fine, I've added couple of cases to tests.
• pydantic was not included for conint and confloat.

Regards
Kamil

[codecov]

Codecov Report

Merging #84 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff          @@
##           master    #84   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files          12     12           
  Lines         697    701    +4     
  Branches      134    135    +1     
=====================================
+ Hits          697    701    +4

Impacted Files	Coverage Δ
...amodel_code_generator/model/pydantic/base_model.py	100% <ø> (ø)	⬆️
datamodel_code_generator/imports.py	100% <100%> (ø)	⬆️
datamodel_code_generator/model/pydantic/types.py	100% <100%> (ø)	⬆️
datamodel_code_generator/parser/openapi.py	100% <100%> (ø)	⬆️

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[koxudaxi]

@krezac
Thank you for creating this PR.
I did not notice the case :(

It looks good 🎉
I have merged into master, and I have released it as version 0.2.16

Thank you very much.