x86: Add int1 as one byte opcode 0xf1

Also change the x86 disassembler to disassemble 0xf1 as int1, instead of
icebp.

gas/

	PR gas/28088
	* testsuite/gas/i386/opcode.s: Add int1.
	* testsuite/gas/i386/x86-64-opcode.s: Add int1, int3 and int.
	* testsuite/gas/i386/opcode-intel.d: Updated.
	* testsuite/gas/i386/opcode-suffix.d: Likewise.
	* testsuite/gas/i386/opcode.d: Likewise.
	* testsuite/gas/i386/x86-64-opcode.d: Likewise.

opcodes/

	PR gas/28088
	* i386-dis.c (dis386): Replace icebp with int1.
	* i386-opc.tbl: Add int1.
	* i386-tbl.h: Regenerate.