TabContainer: implement responsive paddings

[ilhan007]

Is your feature request related to a problem? Please describe.
Support different paddings in the TabContainer, depending on the component size (not screen size).

Left and right margins of the tabstrip (the tabs area) and the content area (below the tabs) should follow the global layout paddings:

S: 1rem; (results in 16px); M: 2rem; L: 2rem; XL: 3rem; XXL: 3rem;
Size S | <= 599px
Size M | >=600px and <= 1023px
Size L | >= 1024px and <= 1439px
Size XL | >= 1440px

Describe the solution you'd like

A private property (could be "size" or similar) that tracks the component size + CSS that is applied accordingly.
The property can be updated in the existing resize handler "_handleHeaderResize".

:host([size="M"])  {
	padding: 0 2rem;
}
:host([size="L"]) {
	padding: 0 2rem;
}
:host([size="XL"])  {
	padding: 3rem;
}

Note: The tabstrip area may require some DOM/CSS refactoring - it is not just changing few paddings.

[ilhan007]

FYI @SAP/ui5-webcomponents-topic-rd