zend_compile: Optimize `sprintf()` into a rope (#14546)

* zend_compile: Add `zend_compile_rope_finalize()`

This just extracts the implementation as-is into a dedicated function to m

zend_compile: Optimize `sprintf()` into a rope (#14546)

* zend_compile: Add `zend_compile_rope_finalize()`

This just extracts the implementation as-is into a dedicated function to make
it reusable in preparation of a future commit.

* zend_compile: Use clearer parameter names for `zend_compile_rope_finalize()`

* zend_compile: Fix `zend_compile_rope_finalize()` for ropes containing a single constant string

Without this Opcache will trigger a use-after-free in
`zend_optimizer_compact_literals()`.

Co-authored-by: Ilija Tovilo <ilija.tovilo@me.com>

* zend_compile: Optimize `sprintf()` into a rope

This optimization will compile `sprintf()` using only `%s` placeholders into a
rope at compile time, effectively making those calls equivalent to the use of
string interpolation, with the added benefit of supporting arbitrary
expressions instead of just expressions starting with a `$`.

For a synthetic test using:

<?php

$a = 'foo';
$b = 'bar';

for ($i = 0; $i < 100_000_000; $i++) {
sprintf("%s-%s", $a, $b);
}

This optimization yields a 2.1× performance improvement:

$ hyperfine 'sapi/cli/php -d zend_extension=php-src/modules/opcache.so -d opcache.enable_cli=1 test.php' \
'/tmp/unoptimized -d zend_extension=php-src/modules/opcache.so -d opcache.enable_cli=1 test.php'
Benchmark 1: sapi/cli/php -d zend_extension=php-src/modules/opcache.so -d opcache.enable_cli=1 test.php
Time (mean ± σ): 1.869 s ± 0.033 s [User: 1.865 s, System: 0.003 s]
Range (min … max): 1.840 s … 1.945 s 10 runs

Benchmark 2: /tmp/unoptimized -d zend_extension=php-src/modules/opcache.so -d opcache.enable_cli=1 test.php
Time (mean ± σ): 4.011 s ± 0.034 s [User: 4.006 s, System: 0.005 s]
Range (min … max): 3.964 s … 4.079 s 10 runs

Summary
sapi/cli/php -d zend_extension=php-src/modules/opcache.so -d opcache.enable_cli=1 test.php ran
2.15 ± 0.04 times faster than /tmp/unoptimized -d zend_extension=php-src/modules/opcache.so -d opcache.enable_cli=1 test.php

This optimization comes with a small and probably insignificant behavioral
change: If one of the values cannot be (cleanly) converted to a string, for
example when attempting to insert an object that is not `Stringable`, the
resulting Exception will naturally not show the `sprintf()` call in the
resulting stack trace, because there is no call to `sprintf()`.

Nevertheless it will correctly point out the line of the `sprintf()` call as
the source of the Exception, pointing the user towards the correct location.

* zend_compile: Eagerly handle empty format strings in `sprintf()` optimization

* zend_compile: Add additional explanatory comments to zend_compile_func_sprintf()

* Add zero-argument test to sprintf_rope_optimization_001.phpt

---------

Co-authored-by: Ilija Tovilo <ilija.tovilo@me.com>

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