fix: correct height and position for inner element

[chintankavathia]

fix datatable-selection element which is not correctly getting height and position.

steps:

• go to any example https://siemens.github.io/ngx-datatable/
• open inspector
• check height and position of datatable-selection element in DOM

What kind of change does this PR introduce? (check one with "x")

• [x] Bugfix
• [ ] Feature
• [ ] Code style update (formatting, local variables)
• [ ] Refactoring (no functional changes, no api changes)
• [ ] Build related changes
• [ ] CI related changes
• [ ] Other... Please describe:

What is the current behavior? (You can also link to an open issue here)

What is the new behavior?

Does this PR introduce a breaking change? (check one with "x")

• [ ] Yes
• [x] No

If this PR contains a breaking change, please describe the impact and migration path for existing applications: ...

Other information:

[spike-rabbit]

Not sure, if this is really the correct fix. In my opinion the actual problem here is, that this is a component, while it should be at a directive.or maybe even just merged into the datatable-scroller which itself should not be a component either.

[spike-rabbit]

@chintankavathia please check if this is still needed. We did some changes around this.

[chintankavathia]

Not needed anymore