Add readKey sequence timeout

[prateekbhujel]

This lets callers tune how long Terminal::readKey() waits for bytes that complete an escape / UTF-8 sequence after the first byte.

The default stays 25ms. Passing a longer sequence timeout helps slow SSH/PTY cases where Esc arrives before the rest of an arrow-key sequence.

Changed:

• add optional $sequenceTimeout to Terminal::readKey()
• keep Windows runtime behavior unchanged because Windows reads key events, not escape bytes
• add POSIX pty coverage for a delayed arrow-key sequence
• remove the Windows master CI leg because php.net now publishes master deps under VS18 while php/php-windows-builder@v1 still requests the missing VS17 package URL; Unix nightly and Windows 8.2-8.5 TS/NTS coverage stay in place

Tested:

• make test REPORT_EXIT_STATUS=1 NO_INTERACTION=1 TEST_PHP_EXECUTABLE=/Applications/XAMPP/xamppfiles/bin/php (12/12 passed)