Faster MapBuilder::build()

[staabm]

testing with https://github.com/staabm/php-code-coverage-bug1062 reveleaed:

before 6afb0db we fatal errored

➜  php-code-coverage-bug1062 git:(main) vendor/bin/phpunit --coverage-text --only-summary-for-coverage-text tests/Test.php
PHPUnit 12.3.7 by Sebastian Bergmann and contributors.

Runtime:       PHP 8.3.24 with Xdebug 3.4.5
Configuration: /Users/staabm/workspace/php-code-coverage-bug1062/phpunit.dist.xml

MobileServiceApi2018093110807480PHP Fatal error:  Allowed memory size of 3439329280 bytes exhausted (tried to allocate 1073741832 bytes) in /Users/staabm/workspace/php-code-coverage-bug1062/vendor/phpunit/php-code-coverage/src/Target/MapBuilder.php on line 167

Fatal error: Allowed memory size of 3439329280 bytes exhausted (tried to allocate 1073741832 bytes) in /Users/staabm/workspace/php-code-coverage-bug1062/vendor/phpunit/php-code-coverage/src/Target/MapBuilder.php on line 167

---

since 6afb0db we de-duplicate the array contents earlier which means less memory required while working -> we ran the repro without fatal error

➜  php-code-coverage-bug1062 git:(main) vendor/bin/phpunit --coverage-text --only-summary-for-coverage-text tests/Test.php
Xdebug: [Step Debug] Could not connect to debugging client. Tried: 127.0.0.1:9003 (through xdebug.client_host/xdebug.client_port).
PHPUnit 12.3.7 by Sebastian Bergmann and contributors.

Runtime:       PHP 8.3.24 with Xdebug 3.4.5
Configuration: /Users/staabm/workspace/php-code-coverage-bug1062/phpunit.dist.xml

F                                                                   1 / 1 (100%)

Time: 00:00.072, Memory: 22.00 MB
...

---

with this PR we prevent unnecessary work and run twice as fast as with 6afb0db

➜  php-code-coverage-bug1062 git:(main) vendor/bin/phpunit --coverage-text --only-summary-for-coverage-text tests/Test.php
Xdebug: [Step Debug] Could not connect to debugging client. Tried: 127.0.0.1:9003 (through xdebug.client_host/xdebug.client_port).
PHPUnit 12.3.7 by Sebastian Bergmann and contributors.

Runtime:       PHP 8.3.24 with Xdebug 3.4.5
Configuration: /Users/staabm/workspace/php-code-coverage-bug1062/phpunit.dist.xml

F                                                                   1 / 1 (100%)

Time: 00:00.039, Memory: 22.00 MB
...

[staabm]

with the last commit I think the implementation got a bit easier.
it uses the same fast-path for all cases now and renders the reproducer even faster and with even less memory:

➜  php-code-coverage-bug1062 git:(main) vendor/bin/phpunit --coverage-text --only-summary-for-coverage-text tests/Test.php
Xdebug: [Step Debug] Could not connect to debugging client. Tried: 127.0.0.1:9003 (through xdebug.client_host/xdebug.client_port).
PHPUnit 12.3.7 by Sebastian Bergmann and contributors.

Runtime:       PHP 8.3.24 with Xdebug 3.4.5
Configuration: /Users/staabm/workspace/php-code-coverage-bug1062/phpunit.dist.xml

F                                                                   1 / 1 (100%)

Time: 00:00.032, Memory: 18.00 MB
...