fix(select): make options list same width as button

[yggg]

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:

Fixes case when nb-select itself has padding leading to overlay being disconnected from a button or having width more than a button.

[codecov]

Codecov Report

Merging #1650 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master    #1650   +/-   ##
=======================================
  Coverage   83.54%   83.54%           
=======================================
  Files         231      231           
  Lines        7560     7560           
  Branches      663      663           
=======================================
  Hits         6316     6316           
  Misses       1051     1051           
  Partials      193      193

Impacted Files	Coverage Δ
...mework/theme/components/select/select.component.ts	86.74% <100%> (ø)	⬆️