TINKERPOP-3023 Expand type syntax in grammar in 3.8 - Remove Vertex

[EchoNullify]

Feat: Remove Vertex support from grammar, and for places where a vertex is required, pass in the vertex id instead at traversal construction.

• The grammar currently includes inconsistencies, particularly around "type constructors" like ReferenceVertex(), which are being re-evaluated.

• ReferenceVertex should be renamed simply to Vertex, as the distinction (e.g., between ReferenceVertex and DetachedVertex) is no longer meaningful or guaranteed.

• The keyword new should be removed from the grammar rule for structureVertex, as it's syntactically unnecessary.

• The Vertex constructor should only require an id, not a label. Labels are not utilized in practice (e.g., in g.V(Vertex)), and can default to an empty string.

Resolves: 3023,

For reference...

https://lists.apache.org/thread/ptq81160z4y4vddg4lxz2nv244x2yzhq

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 79.59184% with 10 lines in your changes missing coverage. Please review.

Please upload report for BASE (3.8-dev@9c7a54c). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
...remlin/process/traversal/step/map/AddEdgeStep.java	64.70%	4 Missing and 2 partials :warning:
...in/language/grammar/DefaultGremlinBaseVisitor.java	0.00%	2 Missing :warning:
...n/process/traversal/step/map/AddEdgeStartStep.java	87.50%	2 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             3.8-dev    #3133   +/-   ##
==========================================
  Coverage           ?   76.52%           
  Complexity         ?    13829           
==========================================
  Files              ?     1109           
  Lines              ?    69787           
  Branches           ?     7545           
==========================================
  Hits               ?    53404           
  Misses             ?    13617           
  Partials           ?     2766           

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[Cole-Greer]

I've pushed some changes into the branch which updates the docs a bit and strips out the vertex -> id sugar in GraphTraversal as it's not required for bytecode. (to be added to master in a separate PR)

My vote is VOTE +1

[Cole-Greer]

Note: Followup PR for master: https://github.com/apache/tinkerpop/pull/3138