Style more output of "disassemble" command

I noticed a couple of spots where the "disassemble" could style its
output, but currently does not.  This patch adds styling to the
function name at the start of the disassembly, and any addresses
printed there.

gdb/ChangeLog
2020-10-08  Tom Tromey  <tom@tromey.com>

	* cli/cli-cmds.c (print_disassembly): Style function name and
	addresses.  Add _() wrappers.

gdb/testsuite/ChangeLog
2020-10-08  Tom Tromey  <tom@tromey.com>

	* gdb.base/style.exp: Check that "main"'s name is styled.