Improve logging on build failure by displaying file contents of `meson-log.txt`

The current output from `pip` when encountering a build error is very poor. gh-231 will fix one part of that, by reducing the traceback of irrelevant pip/meson-python internals. There is a second part however which we need to improve on, which is showing the actual root cause of a build failure when possible. Now what happens is the user sees something like:

```
../../scipy/meson.build:40:0: ERROR: Command "/usr/bin/python3 -c import os; os.chdir(".."); import numpy; print(numpy.get_include())" failed with status 1.

A full log can be found at /tmp/pip-install-3okqoo15/scipy_a5afe2fae16c4250875f20d9db43706f/.mesonpy-u88p7q3f/build/meson-logs/meson-log.txt
```
and is then left wondering "_why does `import numpy` fail, given `numpy` is a build dependency?"_. The answer is in `meson-log.txt`, which `pip` has unhelpfully already cleaned up. So it's impossible to diagnose the issue (latest example for scipy [here](https://github.com/scipy/scipy/issues/16784#issuecomment-1352898268)).

Two options to improve here that I can think of:
1. Don't clean up the log file
2. Print to log file contents to stdout (possibly followed by repeating the root cause from the original stdout content)

(2) is probably better than (1).

Beginne damit nachzuverfolgen, wie Build-Fehler von pip aus Meson gemeldet und bereinigt werden, und verwende dabei den im Issue angegebenen Pfad meson-log.txt. Vergleiche das Aufbewahren des Logs mit der Anzeige seines Inhalts auf stdout und reproduziere einen fehlschlagenden Build, um die verfügbare Ausgabe zu untersuchen. Die Aufgabe ist erledigt, wenn Benutzer die Ursache auch diagnostizieren können, nachdem das temporäre Build-Verzeichnis bereinigt wurde.

Vom Indexierungsmodell aus dem Issue-Text verfasst.