Clarify FWECorrector arguments

[adelavega]

The FWECorrector was written generally, such that methods beyond bonferoni and montecarlo could be specified if an Estimator implements one.

However, as of yet no such alternate method is implemented, and this generic organization obfuscates the API for the FWECorrector, as its not clear what possible options are implmeneted by estimators for monte carlo correction.

Here, I make this API more explicit by:

• Makes montecarlo and bonferroni only possible options for FWECorrector, instead of any possible yet to defined method
• Sets n_iters to 5000 across the board (except MKDAChi2)
• Makes other montecarlo arguments directly available to FWECorrector

[jdkent]

could n_iters be set in the base_class?

https://github.com/neurostuff/NiMARE/pull/865/files#diff-4cafb2c711a65e5b19450202efbd9250dc086c814fb97588c1fd88afcc1add0cL73-L80

could save having to keep track of the default value in multiple locations

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (efae75e) 88.48% compared to head (98b4bd8) 88.20%.
Report is 6 commits behind head on main.

Files	Patch %	Lines
nimare/correct.py	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #865      +/-   ##
==========================================
- Coverage   88.48%   88.20%   -0.29%     
==========================================
  Files          48       48              
  Lines        6337     6339       +2     
==========================================
- Hits         5607     5591      -16     
- Misses        730      748      +18     

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