refactor: rename union/minus node expressions to join/remove in node … (#636)

* refactor: rename union/minus node expressions to join/remove in node expression spec

* feat: add advanced sequence operations (flatMap, findFirst, matchAll) to node expressions

* docs: add newlines and minor whitespace improvements in node expressions spec

* docs: update SHACL vocabulary comments to reflect join/remove terminology

* refactor: rename minus/union node expressions to remove/join in shnex vocabulary

* feat: add vocabulary definitions for flatMap, findFirst, and matchAll node expressions

* docs: clarify distinction between sh:path and shnex:pathValues in node expressions spec

* docs: remove redundant description from Advanced Sequence Operations section

* chore: apply fixes proposed by Ted

Co-authored-by: Ted Thibodeau Jr <tthibodeau@openlinksw.com>

* chore: apply suggested fix to wording

* fix: replace leftover 'union' with 'join'

* refactor: rename Join expressions to Concat expressions in vocabulary and documentation

* enhance: add examples for shnex:concat and shnex:remove expressions in documentation

* enhance: add evaluation traces for various sequence operations

* fix: update deprecation comments for sh:union to reference shnex:concat

* Apply suggestions from code review

Co-authored-by: Ted Thibodeau Jr <tthibodeau@openlinksw.com>
Co-authored-by: Holger Knublauch <holger@topquadrant.com>

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Co-authored-by: Ted Thibodeau Jr <tthibodeau@openlinksw.com>
Co-authored-by: Holger Knublauch <holger@topquadrant.com>

Author: 3 people