Enable relevant XZ decoding options in kernel by default

Nobody has claimed this yet.

**Is your feature request related to a problem? Please describe.**
Modern distributions (e.g. RH) enable
CONFIG_XZ_DEC_X86=y
CONFIG_XZ_DEC_POWERPC=y
CONFIG_XZ_DEC_IA64=y
CONFIG_XZ_DEC_ARM=y
CONFIG_XZ_DEC_ARMTHUMB=y
CONFIG_XZ_DEC_SPARC=y
CONFIG_XZ_DEC_BCJ=y
in their kernel configuration.
This allows them to mount squashfs filesystems created anywhere.
Default WSL kernel returns IO error with a 'helpful' message of
```
[ 1454.847511] SQUASHFS error: xz decompression failed, data probably corrupt
[ 1454.847907] SQUASHFS error: Failed to read block 0x5c3cb5e: -5
```
recompiling the WSL kernel with above settings fixes the problem.

**Describe the solution you'd like**
Enabling the kernel compilation options is a low-cost solution not leading to code bloat and allows to process various squashfs entries with default WSL kernel.

**Describe alternatives you've considered**
given that squashfs may come from any source, alternative is to unpack squashfs with userlevel tools before using.
squashfs could have high compression ratios, resulting in unneededly high disk usage.

**Additional context**
none

Thanks.

Start by locating the WSL kernel configuration and the existing SquashFS/XZ settings. Enable the listed CONFIG_XZ_DEC_* options, build the kernel, and verify that SquashFS images using the relevant XZ filters can be mounted without the reported decompression error.

Written by the indexing model from the issue text.