[EuiInlineEdit] Create placeholder prop for Inline Edit compoents

[breehall]

Is your feature request related to a problem? Please describe.
The inline edit pattern in Stack Management is similar to the EuiInlineEdit component, however, it has two display options for readMode. It can either:

• Display a default value that populates the field text form control in editMode
• Display a placeholder value that does not populate the field text form control in editMode

Component Reference: <InlineTextInput />
Path: x-pack/plugins/ingest_pipelines/public/application/components/pipeline_editor/components/pipeline_processors_editor_item/inline_text_input.tsx

Describe the solution you'd like

• Create a boolean prop to determine if the default value should be displayed as a placeholder or not
• When the boolean is set to true, the editMode field text value will default to an empty string.
  Consumers will still need to implement validation to ensure that empty values cannot be stored.

Additional context
Related to #6778