analyzer: skip constant pool in -fdump-analyzer-untracked [PR testsuite/105085]

In r12-7809-g5f6197d7c197f9 I added -fdump-analyzer-untracked as support
for DejaGnu testing of an optimization of -fanalyzer,
PR analyzer/104954.

PR testsuite/105085 notes testsuite failures of the form:
  FAIL: gcc.dg/analyzer/untracked-1.c (test for excess errors)
  Excess errors:
  cc1: warning: track '*.LC1': yes
where these warnings are emitted on some targets where the test
causes labelled constants to be created in the constant pool.

We probably ought not to be tracking the values of such decls in the
store, given that they're meant to be constant, and I attempted various
fixes to make the "should we track this decl" logic smarter, but given
that we're in stage 4, the simplest fix seems to be for
-fdump-analyzer-untracked to skip such decls in its output, to minimize
test output differences between targets.

gcc/analyzer/ChangeLog:
	PR testsuite/105085
	* region-model-manager.cc (dump_untracked_region): Skip decls in
	the constant pool.

gcc/testsuite/ChangeLog:
	PR testsuite/105085
	* gcc.dg/analyzer/untracked-1.c: Add further test coverage.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>