RISC-V: Add ZCMP push/pop testcases.

Add Zcmp extension testcases, zcmpe means Zcmp with RVE extension.

Co-Authored by: Nandni Jamnadas <nandni.jamnadas@embecosm.com>
Co-Authored by: Yulong Shi <yulong@iscas.ac.cn>
Co-Authored by: Shihua Liao <shihua@iscas.ac.cn>
Co-Authored by: Sinan Lin <sinan.lin@linux.alibaba.com>

gcc/testsuite/ChangeLog:

        * gcc.target/riscv/zc-zcmp-push-pop-1.c: New test.
        * gcc.target/riscv/zc-zcmp-push-pop-2.c: New test.
        * gcc.target/riscv/zc-zcmp-push-pop-3.c: New test.
        * gcc.target/riscv/zc-zcmp-push-pop-4.c: New test.
        * gcc.target/riscv/zc-zcmp-push-pop-5.c: New test.
        * gcc.target/riscv/zc-zcmp-push-pop-6.c: New test.
        * gcc.target/riscv/zc-zcmp-push-pop-7.c: New test.
        * gcc.target/riscv/zc-zcmpe-push-pop-1.c: New test.
        * gcc.target/riscv/zc-zcmpe-push-pop-2.c: New test.
        * gcc.target/riscv/zc-zcmpe-push-pop-3.c: New test.
        * gcc.target/riscv/zc-zcmpe-push-pop-4.c: New test.
        * gcc.target/riscv/zc-zcmpe-push-pop-5.c: New test.
        * gcc.target/riscv/zc-zcmpe-push-pop-6.c: New test.
        * gcc.target/riscv/zc-zcmpe-push-pop-7.c: New test.