Revert breaking change of TypeMap.get_container_cls function header

[rly]

Motivation

#555 introduced a breaking change in the function header for TypeMap.get_container_cls, where the namespace and data_type arguments were swapped and namespace was made optional. Initially, this was thought to be OK for a minor release because this undocumented function is used internally within HDMF and externally only by pynwb.get_class. Given the tight relationship between our development of HDMF and PyNWB, we thought we would simply update PyNWB to address this breaking change. Although we are doing that, the versions of HDMF (>=2.1.0, <3) allowed by the current release of PyNWB (1.4.0) rely on the fact that all releases of HDMF up to version 3 would be compatible with this release of PyNWB. In other words, dependency versioning in PyNWB relies on the policy that breaking changes would occur only in major version bumps. Since that policy was not followed strictly, now PyNWB 1.4.0 is broken for all versions of HDMF 2.5.0 and up and users would not know that when they update HDMF but not PyNWB.

Proposed solution (this PR): Effectively revert these breaking changes for now and re-add them for the next major release. These breaking changes are not critical and we can add the new function as get_dt_container_cls before changing or removing the old get_container_cls. Make a new bugfix release 2.5.1 and perhaps remove 2.5.0 from PyPI and conda-forge.

See also #580 and AllenInstitute/AllenSDK#2098 .

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