build: Add Catch2 dependency.

[Bill-hbrhbr]

Description

highest-order-bit: task build:all ensures that all dependencies are installed before building ystdlib-cpp itself, and it should trigger a re-run whenever there's a dependency change.

• Download and install Catch2 dependency with the newest cmake and remote tasks in yscope-dev-utils.
• Replace the current cmake config and build tasks in ystdlib-cpp with the newest versions in yscope-dev-utils.
• Change the dummy target to a Catch2 unit test target.
• Remove submodules as a potential folder to exclude when linting yaml files in ystdlib-cpp. Now every non-project file resides in build except for yscope-dev-utils.
• Update the lint:venv task to comply with the arglist of new checksum tasks in yscope-dev-utils.
• Add .clang-format in ystdlib-cpp/src for header includes reorder rules.

As discussed offline, we are going to resolve the unnecessarily long dependency installation logs in the future.

Checklist

• The PR satisfies the contribution guidelines.
• This is a breaking change and that has been indicated in the PR title, OR this isn't a
  breaking change.
• Necessary docs have been updated, OR no docs need to be updated.

Validation performed

• The new unit test target builds and runs succcessfully.

[Bill-hbrhbr]

Replied to all comments. Implementations will come shortly after.