feat(toastr): add toasts limit

[elupanov]

Please read and mark the following check list before creating a pull request:

• I read and followed the CONTRIBUTING.md guide.
• I read and followed the New Feature Checklist guide.

Short description of what this resolves:

Adds the possibility to limit visible toasts.

[codecov]

Codecov Report

Merging #1637 into master will increase coverage by 0.08%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1637      +/-   ##
==========================================
+ Coverage   83.46%   83.54%   +0.08%     
==========================================
  Files         231      231              
  Lines        7552     7560       +8     
  Branches      661      663       +2     
==========================================
+ Hits         6303     6316      +13     
+ Misses       1055     1051       -4     
+ Partials      194      193       -1

Impacted Files	Coverage Δ
...ramework/theme/components/toastr/toastr.service.ts	90.51% <100%> (+5.19%)	⬆️
...framework/theme/components/toastr/toastr-config.ts	95.23% <100%> (+0.23%)	⬆️