ENH: Support passing depletion reader settings at construction

[drewejohnson]

Not really a deprecation yet but this is my first step into #339. The depletion reader can be fully configured at construction like

r = DepletionReader(
    "case_dep.m",
    materials=["f.*"],
    materialVariables=["ADENS", "INH_TOX"],
    metadataKeys=["NAMES", "DAYS"]],
    processTotal=False,
)
r.read()

All of the arguments are optional, defaulting to None. If not given, the values in the rc global settings object is used.

Starting small because I want to get buy in from @DanKotlyar and other users before applying this approach to all the readers.

Current plan roll out (to be re-posted into #339) is

1. next release : each reader can be fully configured at construction. rc unchanged
2. +1 major release : setting any value in the rc object raises a deprecation warning. transition tests away from using rc in favor of direct construction
3. +3 major releases : remove the rc object from the code base

This should give enough time for users to update their applications to move away from the rc object

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• PR fits the project scope
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TODO

• Add something to the changelog (0.11.0?)
• Add a versionadded tag in the docstrings for these parameters

[DanKotlyar]

I like this approach a lot.

[drewejohnson]

@DanKotlyar thanks! Let's let this sit for a few more days to try to get some more feedback. I think this is a good step, but want to give people the chance to chime in on the potential removal of the global rc object

[drewejohnson]

@DanKotlyar ready for your re-review and merge if approved