What does this PR do?

Closes #625

This PR is extremely huge, but actually haven't changed any function of building. To sum up, I divided changes into several commits, recommends that reviewing by commits.

Description of major commits:

• Remove all @throws PHPDoc, it's almost useless for SPC anymore: Don't need to review, it just removed all @throws tag from code.
• Refactor all exception classes, remove unclear RuntimeException, InvalidArgumentException: changes all exception classes in SPC\exception namespace.
• Refactor shell utilities: reorganize namespaces and introduce Shell base class: Make WindowsCmd and UnixShell both extends Shell, which contains several shared methods.
• Introduce AttributeMapper for managing extensions and doctor attributes: Prepare for 3.0, make attribute loading functions into dedicated class.
• Refactor all (except command) modules using new exceptions: This may be quite complicated. Generally speaking, it replaces all Exception class names except those in the command class with the new class name.
• Refactor all command class exception handling: Refactor all command exception handler.
• Remove craft.log: After introducing log/, we don't need craft.log anymore.
• Chore: Some code cleaning up.

As for why not 2.8.0, just because this is not introducing any additional feature for building.

Checklist before merging

If your PR involves the changes mentioned below and completed the action, please tick the corresponding option.
If a modification is not involved, please skip it directly.

• If you modified *.php or *.json, run them locally to ensure your changes are valid:
  • composer cs-fix
  • composer analyse
  • composer test
  • bin/spc dev:sort-config
• If it's an extension or dependency update, please ensure the following:
  • Add your test combination to src/globals/test-extensions.php.
  • If adding new or fixing bugs, add commit message containing extension test or test extensions to trigger full test suite.