GH-4129: Fix rdf:reifies triple dropped when pre-bound variable is used inside an RDF 1.2 annotation

[adityaanikam]

GitHub issue resolved #4129

Pull request Description:

QueryTransformOps.replaceVars() (used to pre-bind a variable at the AST level,
before query execution) drops the rdf:reifies triple generated by an RDF 1.2
{| ... |} annotation when the variable being substituted is used inside the
reified triple.

Root cause: in QueryTransformOps.mutateByQueryType()'s CONSTRUCT case, each
quad's subject/predicate/object goes through transformOrSame(Node, ExprTransform).
That method only checked Var.isVar(node) and returned any non-Var node
unchanged. The rdf:reifies triple's object is a quoted triple term
(Node_Triple) that itself contains the variable, not a plain Var, so it was
never substituted. The separate base triple did substitute correctly (its
subject is a plain Var), which is why the bug report shows the base triple
correct but the rdf:reifies triple missing entirely from the CONSTRUCT
output - it still held an unbound variable and was silently dropped when the
template was later instantiated.

The fix adds triple-term recursion to transformOrSame, mirroring the existing,
correct pattern already used at query-execution time in
org.apache.jena.sparql.core.Substitute.substitute(Node, Binding) (which is why
substituting via a WHERE-clause binding already worked, per the original report).

A new regression test, transformTransformReplace_reifies_01 in
TestQuerySyntaxTransform, reproduces the exact query from the issue and
asserts both the base triple and the rdf:reifies triple's quoted triple have
the substitution applied.

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• Tests are included.
• Documentation change and updates are provided for the Apache Jena website - not applicable, internal bug fix with no user-facing behavior change to document.
• Commits have been squashed to remove intermediate development commit messages.
• Key commit messages start with the issue number (GH-xxxx)

By submitting this pull request, I acknowledge that I am making a contribution to the Apache Software Foundation under the terms and conditions of the Contributor's Agreement.

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See the Apache Jena "Contributing" guide.

[afs]

A couple of suggested tweaks but otherwise looks good.