[5.3] Implement blade macros feature

[reshadman]

Please see: #16525

Summary:

Using @include directive only for abstraction on large iterations(for instance a collection) causes increasing render time due to the use of native include feature. the purpose of an @include in these situations is to satisfy the Don't repeat yourself problem but it increases render time even when opcache is fully enabled. In addition to this, lots of view events are fired(creating, composing) and lots of try/catch blocks are used.

Solution:

• Creating a new directive called @macro
• Reading the file content of the macro from the STRING given to the @macro directive
• Wrapping the content around a self-callable function to satisfy scoped data
• Replacing the directive with the new generated content.

Problems:
Because of pasting the generated code inside the original view, file changes to the macro template are not detected, so views should be always cleared for each request in development environments.

[taylorotwell]

This is just quite complicated. You may be able to write it as a Blade directive to do what you want.