CustomSelectControlV2: fix item styles

[ciampo]

What?

Part of #55023

Fix items (options) styles of CustomSelectControlV2 component

Why?

• To fix visual bugs
• To match more closely look of V1 component
• To add quality of life improvements

How?

• Update V2 items in order to match the same line height of the V1 version
• Add disabled styles
• Added user-select: none to trigger button and option items
• Added scroll-margin to improve scroll experience when selecting items that are out of view in the popover

Testing Instructions

• Compare V1 and V2 (legacy) of CustomSelectControl, make sure that the items in the select popover now render with the same line height (28px).
• Try to select with the cursor the text of the items in the select popover — V2 should prevent text selection

V1	V2 before (trunk)	V2 after (this PR)

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Co-authored-by: ciampo <[email protected]>
Co-authored-by: mirka <[email protected]>
Co-authored-by: tyxla <[email protected]>

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