Delaying error handlers

Description

Due to error handlers, some operations may have unsuspected effects. This is the cause of bugs and workarounds. Quoting GH-6903:

[...] long-standing source of interrupt
vulnerabilities: A notice is emitted during execution of an opcode,
resulting in an error handling being run. The error handler modifies
some data structure the opcode is working on, resulting in UAF or
other memory corruption.

These bugs and workarounds could be avoided by delaying error handlers until a safepoint. Existing/Previous work:

• https://github.com/php/php-src/pull/6903
• https://github.com/php/php-src/pull/7735
• https://github.com/php/php-src/pull/12090
• https://github.com/php/php-src/pull/12805

I'm creating this ticket to aggregate issues that would not exist with delayed error handlers:

• https://github.com/php/php-src/issues/13754
• https://github.com/php/php-src/issues/15907
• https://github.com/php/php-src/issues/16726
• https://github.com/php/php-src/issues/17416
• https://github.com/php/php-src/issues/18043
• https://github.com/php/php-src/issues/18274
• https://github.com/php/php-src/issues/20042
• https://github.com/php/php-src/issues/20482
• https://github.com/php/php-src/issues/20855
• https://github.com/php/php-src/issues/21024
• https://github.com/php/php-src/issues/21245

まず、以前の pull request 6903、7735、12090、12805 を確認し、次にここにまとめられているリンク先の issue を調査します。エラーハンドラーが safepoint まで遅延され、一覧にある割り込み関連のバグと workaround が適用されなくなれば、作業は完了です。