pcre2: Update to upstream version 10.42 (reverted)

[akien-mga]

Changelog: https://github.com/PCRE2Project/pcre2/blob/pcre2-10.42/ChangeLog

This should also fix support for RISC-V architectures, at least in the sljit library.
@aaronfranke Could you test and confirm?

I see that upstream sljit is fairly active still improving riscv support (https://github.com/zherczeg/sljit/commits/master), so it might be that the current snapshot as of pcre2 10.42 doesn't work fully yet. If so we can postpone enabling the lib on RISC-V to a future release (or maybe keep building the regex module, but just disable JIT with env["builtin_pcre2_with_jit"], as we already do for Web).

[aaronfranke]

This compiles on RISC-V (scons use_llvm=yes on a rv64gc virtual machine / emulator).

[vonagam]

This PR caused those lines to appear (repeated multiple times) in unit tests logs at the start.

ERROR: Condition "p_ptr == nullptr" is true.
   at: free_static (core/os/memory.cpp:148)

While tests do not fail because of that, this does not seem right...
Or is it unavoidable known issue?

[akien-mga]

Backtrace:

(gdb) bt
#0  Memory::free_static (p_ptr=0x0, p_pad_align=false) at core/os/memory.cpp:149
#1  0x0000000006c247fb in _regex_free (ptr=0x0, user=0x0) at modules/regex/regex.cpp:43
#2  0x0000000006c1cb84 in pcre2_match_32 (code=0xc9019b0, subject=0xc8a74c0, length=9, start_offset=0, options=0, match_data=0xc830060, mcontext=0xc9863b0) at thirdparty/pcre2/src/pcre2_match.c:6846
#3  0x0000000006c25c85 in RegEx::search (this=0x7fffffffc300, p_subject=..., p_offset=0, p_end=-1) at modules/regex/regex.cpp:219
#4  0x00000000057cfee7 in TestRegEx::DOCTEST_ANON_FUNC_6556 () at ./modules/regex/tests/test_regex.h:81
#5  0x00000000053d282d in doctest::Context::run (this=0x7fffffffd0e0) at ./thirdparty/doctest/doctest.h:6930
#6  0x00000000057d5540 in test_main (argc=2, argv=0x7fffffffd728) at tests/test_main.cpp:174
#7  0x0000000005393ec2 in Main::test_entrypoint (argc=2, argv=0x7fffffffd728, tests_need_run=@0x7fffffffd1bf: true) at main/main.cpp:608
#8  0x0000000005333cc2 in main (argc=2, argv=0x7fffffffd728) at platform/linuxbsd/godot_linuxbsd.cpp:55

It probably comes from this change:

9. Removed the use of an initial backtracking frames vector on the system stack
in pcre2_match() so that it now always uses the heap. (In a multi-thread
environment with very small stacks there had been an issue.) This also is
tidier for JIT matching, which didn't need that vector. The heap vector is now
remembered in the match data block and re-used if that block itself is re-used.
It is freed with the match data block.

We likely need to change our _regex_free (and maybe _regex_malloc) to take this new heap vector into account somehow.

[akien-mga]

I reverted the change for now with d0398f6. I'll reopen the PR as a draft until we find how to change modules/regex/regex.cpp to take the internal memory change into account.