Upgrade FlatBuffers to 25.9.23 and use TypeScript workflow

[afarber]

Fix #7235 by:

• Upgrade FlatBuffers from 24.3.25 to 25.9.23
• Switch from "flatc --js" to "flatc --ts" with transpilation to Javascript
• Update the import paths in test files

Tasklist

• CHANGELOG.md entry (How to write a changelog entry)
• update relevant Wiki pages
• add tests (see testing documentation)
• review
• adjust for comments

Requirements / Relations

Link any requirements here. Other pull requests this PR is based on?

[afarber]

Hi @SiarheiFedartsou, hi @DennisOSRM please review my PR.

flatc does not support generating Javascript files anymore, so I transpile Typescript to Javascript.

[afarber]

Hi @DennisOSRM and @SiarheiFedartsou please review my PR.

The PR modifies many files in the third_party/flatbuffers folder.

To verify, that I have not introduced any "trojan horses", you could run:

  git clone --depth 1 --branch v25.9.23 https://github.com/google/flatbuffers.git /tmp/flatbuffers-official

  for dir in include src CMakeLists.txt; do
    echo "=== Comparing $dir ==="
    diff -r "third_party/flatbuffers/$dir" "/tmp/flatbuffers-official/$dir" \
      --exclude='*.o' --exclude='*.so' --exclude='CMakeFiles' \
      --exclude='*.cmake' --exclude='Makefile' 2>/dev/null || echo "No differences"
  done