[pegtl] Update to 3.0.0 release

[wravery]

Describe the pull request

• What does your PR fix?

https://github.com/taocpp/PEGTL just released version 3.0.0. This syncs the vcpkg port with that release tag.

• Which triplets are supported/not supported? Have you updated the CI baseline?

This is a header-only library with no dependencies outside of the C++17 standard library. It does require std::filesystem, but it has fallback logic in CMake to auto-detect the std::experimental::filesystem implementation or additional linked library requirements that are required on older toolchains.

• Does your PR follow the maintainer guide?

Yes.

[JackBoosY]

/mnt/vcpkg-ci/installed/x64-linux/include/tao/pegtl/read_input.hpp:7:10: fatal error: filesystem: No such file or directory
 #include <filesystem>
          ^~~~~~~~~~~~
compilation terminated.

See https://stackoverflow.com/questions/39231363/fatal-error-filesystem-no-such-file-or-directory.
Can you please fix it in this PR?

Thanks.

[JackBoosY]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[JackBoosY]

No achives were found in the results, will rerun the pipeline test.

[wravery]

Trouble is PEGTL has dropped support for those compiler versions (so cppgraphqlgen, which depends on PEGTL did as well) since they don't fully implement C++17. To fix it would mean patching PEGTL in a way that I don't think the upstream maintainer would want to take. Is it better to patch the port (and see about upstreaming the patch later), or is there a process for deprecating these older compiler toolchains for a given port?

[JackBoosY]

@wravery We want to use the patch method accepted by upstream, do you have any ideas?

[wravery]

We've sort of been discussing this in taocpp/PEGTL#216, I have an idea that might work. Let me see if the project owners like it.

[wravery]

Accidentally force pushed the reset instead of the replacement.

[BillyONeal]

Thanks for your contribution!