Add package version to metadata

[cottsay]

The package version is typically read during the augmentation phase, but this package doesn't have one (yet). Since the dependencies are already being read during identification, go ahead and read the version then as well.

Here's where this is populated for Python packages: https://github.com/colcon/colcon-core/blob/a74fa97fcea08d1e276a327228c119ce78aa0075/colcon_core/package_augmentation/python.py#L48-L50

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 71.42857% with 2 lines in your changes missing coverage. Please review.

Project coverage is 67.21%. Comparing base (b12c637) to head (1b3f625).

Files with missing lines	Patch %	Lines
colcon_cargo/package_identification/cargo.py	71.42%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #45      +/-   ##
==========================================
+ Coverage   67.09%   67.21%   +0.12%     
==========================================
  Files           6        6              
  Lines         234      241       +7     
  Branches       35       35              
==========================================
+ Hits          157      162       +5     
- Misses         55       57       +2     
  Partials       22       22              

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[luca-della-vedova]

Thanks!