fix: replace variable accounName for cli login (#15694)

[hellyzh]

The ${accountName} placeholders are now replaced with the display name ("M365" or "Azure") before passing the template to MSAL's successTemplate/errorTemplate

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.94%. Comparing base (11924e7) to head (0bd51e1).
⚠️ Report is 2 commits behind head on release/6.8.

Additional details and impacted files

@@               Coverage Diff               @@
##           release/6.8   #15697      +/-   ##
===============================================
- Coverage        92.95%   92.94%   -0.01%     
===============================================
  Files              623      623              
  Lines            38443    38443              
  Branches          6957     6978      +21     
===============================================
- Hits             35735    35732       -3     
  Misses            1979     1979              
- Partials           729      732       +3     

see 2 files with indirect coverage changes

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