[SFrame-V3] gas: x86: testsuite: add new testcases for SFRAME_FDE_TYPE_FLEX

gas/testsuite/
	* gas/cfi-sframe/cfi-sframe-x86_64-4.d: New test.
	* gas/cfi-sframe/cfi-sframe-x86_64-4.s: Non SP/FP based CFA.
	* gas/cfi-sframe/cfi-sframe-x86_64-esc-expr-1.d: New test.
	* gas/cfi-sframe/cfi-sframe-x86_64-esc-expr-1.s: DRAP pattern
	with both CFA expression and FP expression.
	* gas/cfi-sframe/cfi-sframe-x86_64-esc-expr-2.d: New test.
	* gas/cfi-sframe/cfi-sframe-x86_64-esc-expr-2.s: Test CFA
	expression with sleb128.
	* gas/cfi-sframe/cfi-sframe.exp: Add new tests.