Updated recovery key parsing code to not rely on OS specific line endings

[bsclifton]

Fixes #12716

Auditors: @kjozwiak, @NejcZdovc

Submitter Checklist:

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Ran git rebase -i to squash commits (if needed).
• Tagged reviewers and labelled the pull request as needed.
• Request a security/privacy review as needed. (Ask a Brave employee to help if you cannot access this document.)

Automated Test Plan:

npm run unittest -- --grep="loadKeysFromBackupFile"

Test plan

See #12716

Reviewer Checklist:

• Request a security/privacy review as needed if one was not already requested.

Tests

• Adequate test coverage exists to prevent regressions
• Tests should be independent and work correctly when run individually or as a suite ref
• New files have MPL2 license header

[NejcZdovc]

do we need another toString? we are doing it on the line 267

[codecov-io]

Codecov Report

Merging #12717 into master will increase coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master   #12717      +/-   ##
==========================================
+ Coverage   56.09%   56.12%   +0.02%     
==========================================
  Files         279      279              
  Lines       27245    27245              
  Branches     4430     4430              
==========================================
+ Hits        15282    15290       +8     
+ Misses      11963    11955       -8

Flag	Coverage Δ
#unittest	56.12% <100%> (+0.02%)	⬆️

Impacted Files	Coverage Δ
app/browser/api/ledger.js	56.26% <100%> (+0.86%)	⬆️
js/stores/appStoreRenderer.js	91.17% <0%> (-8.83%)	⬇️
app/renderer/components/reduxComponent.js	84.37% <0%> (-6.25%)	⬇️
js/stores/windowStore.js	27.25% <0%> (-0.31%)	⬇️

[NejcZdovc]

++ looks good

Did the following test:

1. clean profile
2. save recovery file
3. change EOL to windows style
4. clean profile
5. import windows style file

[NejcZdovc]

master fa416ba
0.21 b13a380
0.20 b2c0673
0.19 8e59083