Trim white spaces before and after the equal sign

[duke8253]

This fixes #7888

Also cleans up the code for trimming and squeezing spaces.

[SolidWallOfCode]

The original code is terrible, you should take this opportunity to fix it. Foremost, don't use stringstream. Why not something like

std::string out;
out.reserve(in.size());
size_t n = 0;
for ( char c : in ) {
  if (!isspace(c)) { out << c;  ++n; }
}
out.resize(n);
return out;

[duke8253]

[approve ci]

[zwoop]

@duke8253 This PR seems to fix stuff added in #8579, which is not in 9.2.x. Do we really need this for 9.2.x?

[zwoop]

Cherry-picked to v9.2.x, merged both of these fixes. @duke8253 let me know if this is not desirable for 9.2.x.