Improve the failure message reported by assertQueryTrue()

[johnbillion]

When an assertion made with assertQueryTrue() fails, its failure message is quite confusing. It can be made much clearer.

[johnbillion]

With 40411.patch​:

Before:

is_home, is_page is expected to be true. is_single is expected to be false.
Failed asserting that false is true.

After:

is_home is false but is expected to be true.
is_page is false but is expected to be true.
is_single is true but is expected to be false.

[johnbillion]

In 40416:

Build/Test tools: Improve the failure message reported by assertQueryTrue() so it's a little less cryptic.

Fixes #40411