Feature/overriding refresh token timeouts

[rp4fx12]

There might be a better approach here (or this may not be desired or needed at all) but this should allow for users to override the advisory and mandatory refresh timeouts that are a part of the RefreshableToken Class - addresses this issue: #2189

[codecov-io]

Codecov Report

Merging #2190 into develop will decrease coverage by 0.00%. The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop    #2190      +/-   ##
===========================================
- Coverage    98.19%   98.18%   -0.01%     
===========================================
  Files           58       58              
  Lines        10843    10843              
===========================================
- Hits         10647    10646       -1     
- Misses         196      197       +1     

Impacted Files	Coverage Δ
botocore/credentials.py	98.54% <100.00%> (-0.11%)	:arrow_down:

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[aBurmeseDev]

Thank you for submitting this PR. After team discussion, we're going to have to discuss with other SDKs for potential cross-SDK approach to keep it consistent and decided not to consider this one at this time.