Add expected output and explanatory callouts to values()-step docs

[spmallette]

The reference documentation for the values()-step listed three examples against the TinkerPop Crew graph but rendered no output and offered only a single sentence of prose, so the behavior of the step was difficult to predict from the docs alone.

This adds:

• An introductory paragraph explaining that values() returns the values of the requested properties, or of every property when called with no arguments, and noting that a property may be multi-valued or carry meta-properties.
• Numbered callouts on the three examples clarifying that a no-argument values() returns every property value across all keys, that the sample vertex has a multi-valued location property, and that properties('location').values() extracts meta-property values (the startTime and endTime years) rather than the city-name values returned by values('location').
• A note that the order in which property values are returned is not guaranteed.

The examples remain executable, so their output is rendered at build time rather than hand-written. No behavior changes; this is a documentation-only improvement.

[spmallette]

merged on 45bd9c6

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.48%. Comparing base (a28cd1f) to head (dd1eaee).
⚠️ Report is 373 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #3570      +/-   ##
============================================
+ Coverage     76.35%   76.48%   +0.12%     
- Complexity    13424    14292     +868     
============================================
  Files          1012     1036      +24     
  Lines         60341    64608    +4267     
  Branches       7075     7661     +586     
============================================
+ Hits          46076    49415    +3339     
- Misses        11548    12099     +551     
- Partials       2717     3094     +377     

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