Append UUID when test_name is None for perf tool

[AnandInguva]

#28671 uses test_name for metrics publishing but the test_name is optional and can result in a breaking change if not provided. Add uuid if test_name is none

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[AnandInguva]

R : @pranavbhandari24

[codecov]

Codecov Report

Merging #28882 (df6a88c) into master (7531501) will decrease coverage by 0.01%.
Report is 2 commits behind head on master.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master   #28882      +/-   ##
==========================================
- Coverage   72.23%   72.22%   -0.01%     
==========================================
  Files         685      685              
  Lines      101511   101519       +8     
==========================================
+ Hits        73323    73324       +1     
- Misses      26607    26614       +7     
  Partials     1581     1581              

Flag	Coverage Δ
python	82.70% <100.00%> (-0.01%)	⬇️

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Files	Coverage Δ
...hon/apache_beam/testing/analyzers/perf_analysis.py	16.90% <100.00%> (+1.18%)	⬆️

... and 6 files with indirect coverage changes

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[pranavbhandari24]

LGTM

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