Add gcs_avro_to_bigtable yaml blueprint example and e2e test

[derrickaw]

1. Part of Phase 6 - [Task]: YAML - E2E example pipelines for common use cases #35030

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.74%. Comparing base (76f6e6d) to head (9bc2827).
⚠️ Report is 136 commits behind head on master.

Additional details and impacted files

@@              Coverage Diff              @@
##             master   #40484       +/-   ##
=============================================
+ Coverage     56.16%   79.74%   +23.57%     
=============================================
  Files          1124      487      -637     
  Lines        178336    82287    -96049     
  Branches       1489        0     -1489     
=============================================
- Hits         100170    65618    -34552     
+ Misses        75645    16669    -58976     
+ Partials       2521        0     -2521     

Flag	Coverage Δ
go	?
java	?
python	79.74% <ø> (+0.18%)	⬆️

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[github-actions]

Assigning reviewers:

R: @damccorm for label python.
R: @chamikaramj for label yaml.

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[damccorm]

What is our goal in mirroring all of these across both places? Do we intend to keep them totally in sync?

[damccorm]

It looks like we've been doing this for a while, but this seems like an antipattern to me

[damccorm]

Or are we just saying that this has the same functionality as the Java version of this template?

Btw, is there a reason we're back to blueprint terminology? That may be what is confusing me (#39549 (comment))