Refactor the file detection for Revolut

[mincong-h]

This PR fixes https://github.com/mincong-h/finance-toolkit/issues/85 . More precisely,

• [x] It introduces new account types that users must follow when using Revolut.
• [x] It avoids relying on the filenames for detecting accounts because they change sometimes ("en" vs "undefined_undefined"), which is not reliable. Instead, it uses a post-filtering mechanism on field "currency" to matching account.
• [x] It changes the loading logic based on the account type (only take care "cash" accounts as "commodities" accounts' statements cannot be downloaded).

[codecov-commenter]

Codecov Report

Merging #86 (b71fd60) into master (ebd4dbf) will increase coverage by 0.71%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #86      +/-   ##
==========================================
+ Coverage   94.27%   94.98%   +0.71%     
==========================================
  Files          11       11              
  Lines         611      618       +7     
  Branches       98      100       +2     
==========================================
+ Hits          576      587      +11     
+ Misses         20       18       -2     
+ Partials       15       13       -2     

Impacted Files	Coverage Δ
finance_toolkit/pipeline_factory.py	100.00% <100.00%> (+12.50%)	:arrow_up:
finance_toolkit/revolut.py	86.53% <100.00%> (+0.82%)	:arrow_up:

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