Instead of using a temporary file to allow checks with `realpath()` to succeed, use the new `resolve_path()` helper added in a9a629b012 to replace the `realpath()` usage and allow for path resolution of files that don't exist yet.
This will allow new asset files to still be saved correctly, whilst still preventing paths outside of the assets directory to be used.
Replaces b1954e9258.
* Fix loosly comparison to strict + argument types and return types for >=7.0
* Change hard-coded strings to ::class,
* Fix unit-tests failures - some relative to 7.0 phpunit env deployment
* Fix exception string + format return types
* Change string representation of new classes in traceLog to ::class
Credit to @arthurkushman
merdan
Ben Thomson
Luke Towers
Teranode
Nathan van der Werf
Arthur Kushman
Samuel Georges
Szabó Gergő
Stefan Talen