access rules

Validates that PDE correctly adds transitive dependencies to the JDT
classpath with K_NON_ACCESSIBLE access rules (PR #2218). Asserts exact
access rule structure, marker line numbers, problem IDs, severity, and
message patterns for all 24 expected forbidden reference markers.

Also Tests both forbiddenReference=warning (project A) and
forbiddenReference=error (project Ae, JDT default) compiler settings.

Additionally tests of discouraged access tests for x-internal:=true
packages