Fix time api

[goccy]

Since google.protobuf.Timestamp does not have time zone information, when we use withLocation() API, the time zone information may be lost if it bypass Go's value ( timestamppb.Timestamp ).
So, I fix this issue with custom Time message ( it keeps time zone information ).

[github-actions]

Code Metrics Report

	main (c201922)	#235 (18d3c1d)	+/-
Coverage	65.5%	65.5%	-0.0%
Code to Test Ratio	1:0.3	1:0.3	+0.0
Test Execution Time	7m5s	6m50s	-15s

Details

  |                     | main (c201922) | #235 (18d3c1d) |  +/-  |
  |---------------------|----------------|----------------|-------|
- | Coverage            |          65.5% |          65.5% | -0.0% |
  |   Files             |             71 |             71 |     0 |
  |   Lines             |          11825 |          11971 |  +146 |
+ |   Covered           |           7746 |           7837 |   +91 |
+ | Code to Test Ratio  |          1:0.3 |          1:0.3 |  +0.0 |
  |   Code              |          37064 |          37260 |  +196 |
+ |   Test              |          12892 |          12984 |   +92 |
+ | Test Execution Time |           7m5s |          6m50s |  -15s |

Code coverage of files in pull request scope (80.4% → 72.5%)

Files	Coverage	+/-
compiler/compiler.go	79.7%	0.0%
grpc/federation/cel/lib.go	100.0%	0.0%
grpc/federation/cel/time.go	68.3%	-9.0%

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Reported by octocov

[shuheiktgw]

LGTM 🙆‍♂️