Calculating grid's width when initialized with % based on its offsetWidth in IE11(7.0.x)

[HristoP96]

…#3095

Closes #

Additional information (check all that apply):

• Bug fix
• New functionality
• Documentation
• Demos
• CI/CD

Checklist:

• All relevant tags have been applied to this PR
• This PR includes unit tests covering all the new code
• This PR includes API docs for newly added methods/properties
• This PR includes feature/README.MD updates for the feature docs
• This PR includes general feature table updates in the root README.MD
• This PR includes CHANGELOG.MD updates for newly added functionality
• This PR contains breaking changes
• This PR includes ng update migrations for the breaking changes
• This PR includes behavioral changes and the feature specification has been updated with them

[mpavlinov]

This should be fixed on every place that getComputedStyle is used. Extract the code in a function.

[HristoP96]

The changes applied in this PR are merged in 7.0.x through PR 3097. @mpavlinov, after investigating the scenarios in which getComputedStyle is used, only the grid width set with % is broken in IE11.
In IE11 another rendering issue is caused when the grid is set with % and the columns don't have explicit width set. There is an issue about this behavior, which is currently in development.