wg-quick: linux: use sed for trimming config lines

[kkartaltepe]

Bash's longest matching operators combined with extended globs is
extremely slow for very large lines. There are probably very few people
for which this is noticable but in a file with 800 AllowIPs on a single
line it keeps wg-quick from stalling for 5s when performing operations.

I'm not sure about the portability of this to other platforms beyond gnu linux.
My understanding is the multiple -e flag style is the most portable and available
on non-gnu systems but I have not tested.

I didnt see any performance regression but perhaps shelling out to sed is slower
if your config has thousands of lines. I suspect its not.

[kkartaltepe]

Ah sorry right after I sent this i noticed there was a typo and that the non-greedy match in sed was not working...

[kkartaltepe]

Fixed up.