feat(storage): Add ability to restore soft deleted objects

[ddelgrosso1]

Fixes: #13575

This change is 

[ddelgrosso1]

This should be the final piece of #13575 (RestoreObject).

[codecov]

Codecov Report

Attention: Patch coverage is 97.87234% with 5 lines in your changes missing coverage. Please review.

Project coverage is 93.50%. Comparing base (43f595c) to head (73998fd).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
google/cloud/storage/idempotency_policy.h	0.00%	2 Missing ⚠️
...gle/cloud/storage/internal/generic_stub_adapter.cc	0.00%	2 Missing ⚠️
google/cloud/storage/internal/grpc/stub_test.cc	95.65%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #14710      +/-   ##
==========================================
+ Coverage   93.49%   93.50%   +0.01%     
==========================================
  Files        2323     2323              
  Lines      207758   207993     +235     
==========================================
+ Hits       194243   194484     +241     
+ Misses      13515    13509       -6     

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[bajajneha27]

LGTM from my end.

[scotthart]

Reviewed 10 of 32 files at r1.
Reviewable status: 10 of 32 files reviewed, 4 unresolved discussions (waiting on @bajajneha27 and @ddelgrosso1)

---

google/cloud/storage/internal/object_requests.h line 391 at r1 (raw file):

 public:
  RestoreObjectRequest() = default;
  explicit RestoreObjectRequest(std::string bucket_name,

explicit is unnecessary here as the constructor has more than one parameter.