Significant EQL changes in 7.10

[costin]

This ticket serves as a central place for significant changes in EQL to better broadcast them to a larger group.
To keep things simple, please keep the discussions on each individual ticket.

Proposed grammar changes

Case sensitivity - High impact on semantics / rules

Concluded

• Remove any overloading of == including that of wildcards foo == "*.exe". May end up influencing the grammar.
  Issue: EQL: Remove pattern == "wild*card" #62651
• Replace ` with ' (available - see above) for quoting identifiers
  Issues: EQL: Replace ` (back-tick) with ' (single quote) #62663 PR: EQL: Replace [`] with ['] for identifiers #62638
• Replace ?" and ?' for raw string literal """
  Issue: EQL: Replace ?" and ?' with """ #62645 PR: EQL: Replace ?"..." with """...""" for unescaped strings #62539
• Remove case-sensitivity parameter and make EQL case in-sensitive by default - impacted by EQL: Remove pattern == "wild*card" #62651
  Issue: EQL: Revisit case insensitivity #61883 and EQL: Remove case_sensitive option #62255
• Remove ' for string literal declaration and keep only "
  Issue: EQL: changes to strings and regular expressions #61659 PR: EQL: Forbid usage of ['] for string literals #62458
• Disallow 1 == 1 == 1
  Issue: EQL: ambiguous syntax for chained predicates #61654, PR:EQL: Disallow chained comparisons #62567
• Deprecate usage of = for equality checks in favor of ==.
  Issue: EQL: Remove (was Deprecate) = in favor of == for equality checks #62650 PR: EQL: Remove support for = for comparisons #62756

(Edit: @rw-access changed the wording to "Proposed grammar changes" to be more clear)

[elasticmachine]

Pinging @elastic/es-ql (:Query Languages/EQL)

[costin]

All issues have been addressed.