Add troubleshooting block to template readme's

[Polber]

This also regenerates the template README's - this means any files in v1/, v2/, python/ and yaml/ are auto-generated and can be ignored from review.

UPDATE: Added minimal logic (and tests) to skip metadata and image spec generation (as well as skip doc generation) for stage-only images. At this point, the only stage-only image affected is Job Builder image.

[codecov]

Codecov Report

Attention: Patch coverage is 16.66667% with 5 lines in your changes missing coverage. Please review.

Project coverage is 45.09%. Comparing base (babf762) to head (6310ac6).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
.../cloud/teleport/plugin/TemplateSpecsGenerator.java	16.66%	4 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1751      +/-   ##
============================================
+ Coverage     45.04%   45.09%   +0.05%     
- Complexity     3601     3933     +332     
============================================
  Files           835      835              
  Lines         49684    49696      +12     
  Branches       5229     5231       +2     
============================================
+ Hits          22378    22409      +31     
+ Misses        25639    25622      -17     
+ Partials       1667     1665       -2     

Components	Coverage Δ
spanner-templates	66.25% <50.00%> (+0.12%)	⬆️
spanner-import-export	64.20% <50.00%> (+0.38%)	⬆️
spanner-live-forward-migration	76.18% <ø> (ø)
spanner-live-reverse-replication	76.54% <ø> (ø)
spanner-bulk-migration	85.55% <ø> (ø)

Files with missing lines	Coverage Δ
...a/com/google/cloud/teleport/metadata/Template.java	100.00% <ø> (ø)
.../cloud/teleport/plugin/TemplateSpecsGenerator.java	40.49% <16.66%> (+0.66%)	⬆️

... and 5 files with indirect coverage changes