fix(autoware_test_utils): set timestamp in building trajectory msg

[satoshi-ota]

Description

Set stamp so that we can test latency abnormality.

Related links

Parent Issue:

• feat(planning_validator): add diag to check planning component latency autoware.universe#10241

How was this PR tested?

PASS CI/CD

Notes for reviewers

None.

Interface changes

None.

Effects on system behavior

None.

[github-actions]

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[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 9.72%. Comparing base (4cb18f5) to head (0bccc75).
Report is 68 commits behind head on main.

Files with missing lines	Patch %	Lines
...nclude/autoware_test_utils/autoware_test_utils.hpp	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #245       +/-   ##
==========================================
- Coverage   78.75%   9.72%   -69.04%     
==========================================
  Files          11     121      +110     
  Lines         193   10152     +9959     
  Branches       73    1612     +1539     
==========================================
+ Hits          152     987      +835     
- Misses         11    8882     +8871     
- Partials       30     283      +253     

Flag	Coverage Δ
differential	9.72% <0.00%> (?)
total	?

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