[BULK Template] Poc controller

[Deep1998]

This contains dummy code for a POC controller. This uses a FakeReader temporarily to ensure the code builds.

The FakeReader2 and ReaderTransformTestUtils2 are helper classes copied temporarily to use the FakeReader in the main code. This will be removed in the subsequent PR.

Unit tests not added as the public method run needs to complete with actual reader.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 105 lines in your changes are missing coverage. Please review.

Project coverage is 40.48%. Comparing base (b7f8c2b) to head (57b8f96). Report is 54 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1503      +/-   ##
============================================
+ Coverage     40.45%   40.48%   +0.02%     
- Complexity     2749     2773      +24     
============================================
  Files           732      737       +5     
  Lines         41628    41828     +200     
  Branches       4475     4498      +23     
============================================
+ Hits          16842    16932      +90     
- Misses        23319    23419     +100     
- Partials       1467     1477      +10     

Components	Coverage Δ
spanner-templates	55.74% <0.00%> (-0.37%)	:arrow_down:
spanner-import-export	65.57% <ø> (+0.04%)	:arrow_up:
spanner-live-forward-migration	61.23% <ø> (ø)
spanner-live-reverse-replication	42.53% <ø> (ø)
spanner-bulk-migration	68.75% <0.00%> (-1.81%)	:arrow_down:

Files	Coverage Δ
...v2/source/reader/io/transform/ReaderTransform.java	100.00% <ø> (ø)
...oogle/cloud/teleport/v2/templates/FakeReader2.java	0.00% <0.00%> (ø)
...cloud/teleport/v2/templates/SourceDbToSpanner.java	0.00% <0.00%> (ø)
...leport/v2/templates/ReaderTransformTestUtils2.java	0.00% <0.00%> (ø)

... and 21 files with indirect coverage changes