Components: Fix placeholder color inconsistency across SearchControl, TextControl, Inputcontrol

[im3dabasia]

Closes: #64666

What?

This PR ensures a consistent placeholder color across the InputControl, SearchControl, and TextControl components by defining the color explicitly.

Why?

To address the issue where placeholder color varied depending on the applied styles.

How?

The placeholder color has been defined at the component level to avoid inconsistencies and improve accessibility.

Testing Instructions

1. Test the InputControl, SearchControl, and TextControl components in the storybook
2. Ensure the placeholder color is consistent and meets the contrast ratio requirements.

Component	Foreground Color	Background Color
InputControl	#1e1e1e9e (dark gray 62% opacity)	#ffffff (white)
SearchControl	#1e1e1e9e (dark gray 62% opacity)	#f0f0f0 (light gray)
TextControl	#1e1e1e9e (dark gray 62% opacity)	#ffffff (white)

[im3dabasia]

• This PR aims to standardize the placeholder colors for the three components mentioned above. There has been an ongoing discussion about potentially removing the light gray color from the SearchControl, as noted in this issue comment.

• I am happy to take on the task of working on removing the color, if needed.

[github-actions]

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[github-actions]

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Co-authored-by: im3dabasia <[email protected]>
Co-authored-by: t-hamano <[email protected]>

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[im3dabasia]

Hi @t-hamano,

When you have a moment, please review my changes and provide feedback.