Move ItemCollection and derived classes to core

[nselliott]

Summary

• This PR is a refactoring
• It does the following:
  • Moves the ItemCollection and its child classes from Sidre to core, to enable them to be used without depending on the Sidre component.
  • Fixes Move Sidre collections to core #1397 , may be useful within Sina

Moving these header-only classes required removing their dependencies on Slic, as there were a few uses of Slic assertions and warnings. Those have been replaced with raw assert() calls and output to std::cerr, matching what is done elsewhere in Axom core.

The definitions of constants InvalidIndex and InvalidName needed to be moved from Sidre into core for usage by the collection classes.

[rhornung67]

Thanks @nselliott

[kennyweiss]

Thanks @nselliott

Please update the RELEASE_NOTES with this change.
Should add some unit tests to core for basic operations on these classes?

[kennyweiss]

@nselliott -- This function requires the templated type T to have a getName() function.

Could you please document this requirement?
Alternatively, is there a way to conditionally include this function via enable_if ?

[nselliott]

This requirement is documented in the header. I think it's better not to add a SFINAE implementation, as the core feature of MapCollection is to hold a collection of named items. Using enable_if would make the code more complicated and allow instances of MapCollection to compile that don't have a meaningful use case, so in my opinion it's better to catch attempts to do that at compile time.

[nselliott]

Thanks @nselliott

Please update the RELEASE_NOTES with this change. Should add some unit tests to core for basic operations on these classes?

The existing set of unit tests for these classes in the sidre test directory is still good. We could move them to the core test directory if needed.