* Add --ts-undefined-for-optionals command line option
# Details
- Fixes#7656
- Added a new `--ts-undefined-for-optionals` command line option for `flatc`.
- If enabled, generated TypeScript code uses `undefined` for optional fields rather than `null`.
* Also add TS generated test files
* Run `sh scripts/clang-format-git.sh`
* also add tests/ts/lalala-options.ts to the repo
* move new tests to tests/ts/optional_values dir
* add tests/ts/optional_values/optional_values_generated.cjs to the repo
* reuse existing optional_scalars.fbs and add new test
* add comma
* sh scripts/clang-format-git.sh
* remove comma
* sh scripts/clang-format-git.sh
* trying things
* sh scripts/clang-format-git.sh
* done
* address feedback
* sh scripts/clang-format-git.sh
* run `sh scripts/clang-format-git.sh`
* remove uneeded `eslint-disable @typescript-eslint/no-namespace` line
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Co-authored-by: José Luis Millán <jmillan@aliax.net>
