fix: update error handling in Stream::getContents()

[rancoud]

Description

Related to that Pull Request Nyholm/psr7#252

The current implementation of stream_get_contents() swallows errors, leading to issues like symfony/symfony#52490, where errors reported by the stream layer aren't propagated to user-land.

This is even in the C source:
https://github.com/php/php-src/blob/311cae03e730c76aed343312319ed8cf1c37ade0/main/streams/streams.c#L1512

Changelist

• Update Stream::getContents()
• Add tests

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (01d60b3) 100.00% compared to head (7e880b7) 100.00%.

Additional details and impacted files

@@             Coverage Diff             @@
##              master      #169   +/-   ##
===========================================
  Coverage     100.00%   100.00%           
- Complexity       368       370    +2     
===========================================
  Files             11        11           
  Lines            866       875    +9     
===========================================
+ Hits             866       875    +9     

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