[clang][ARM] Enable --print-supported-extensions for ARM (#66083)

```
$ ./bin/clang --target=arm-linux-gnueabihf --print-supported-extensions
<...>
All available -march extensions for ARM

        crc
        crypto
        sha2
        aes
        dotprod
<...>
```

This follows the format set by RISC-V and AArch64. As for AArch64, ARM
doesn't have versioned extensions like RISC-V does. So there is only 1
column, which contains the name.

Any extension without a "feature" is hidden as these cannot be used with
-march.