Fix GH-13071: Copying large files using mmap-able source streams may exhaust available memory and fail

Commit 5cbe5a538c disabled chunking for all writes to streams. However,
user stream

Fix GH-13071: Copying large files using mmap-able source streams may exhaust available memory and fail

Commit 5cbe5a538c disabled chunking for all writes to streams. However,
user streams have a callback where code is executed on data that is
subject to the memory limit. Therefore, when using large writes or
stream_copy_to_stream/copy the memory limit can easily be hit with large
enough data.

To solve this, we reintroduce chunking for userspace streams.
Users have control over the chunk size, which is neat because
they can improve the performance by setting the chunk size if
that turns out to be a bottleneck.

In an ideal world, we add an option so we can "ask" the stream whether
it "prefers" chunked writes, similar to how we have
php_stream_mmap_supported & friends. However, that cannot be done on
stable branches.

Closes GH-13136.

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Deprecate implicit dynamic properties

Writing to a proprety that hasn't been declared is deprecated,
unless the class uses the #[AllowDynamicProperties] attribute or
defines __get()/

Deprecate implicit dynamic properties

Writing to a proprety that hasn't been declared is deprecated,
unless the class uses the #[AllowDynamicProperties] attribute or
defines __get()/__set().

RFC: https://wiki.php.net/rfc/deprecate_dynamic_properties

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Fix some broken or unnecessary CLEAN sections

Don't use chunking for stream writes

We're currently splitting up large writes into 8K size chunks, which
adversely affects I/O performance in some cases. Splitting up writes
doesn't

Don't use chunking for stream writes

We're currently splitting up large writes into 8K size chunks, which
adversely affects I/O performance in some cases. Splitting up writes
doesn't make a lot of sense, as we already must have a backing buffer,
so there is no memory/performance tradeoff to be made here.

This change disables the write chunking at the stream layer, but
retains the current retry loop for partial writes. In particular
network writes will typically only write part of the data for large
writes, so we need to keep the retry loop to preserve backwards
compatibility.

If issues due to this change turn up, chunking should be reintroduced
at lower levels where it is needed to avoid issues for specific streams,
rather than unnecessarily enforcing it for all streams.

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Trim trailing whitespace in tests

test to stream function set_file_buffer.phpt();