Edit embed config to allow overriding the label on the search box

[jwalgran]

Overview

Edit embed config to allow overriding the label on the search box

Depend on model updates in #1533

Describe the solution you'd like

• Update API to allow passing text_search_label when updating EmbedConfig
  • Normalize empty string to null
• Update embedded map UI to add a "Text search label"
  - Include a subsection for 'Custom search text label' under the Fields section of the embed config
  - Info text should describe the use of the custom search text and that it's available when fields are marked searchable
  - Disable the custom search label when no fields are searchable
  - Set the default value to the default search text
  - onBlur, if the text search label is blank, replace it with the default text
  - If at any time no fields are marked searchable, the custom search box is should be reset to the default text and disabled
• Update search sidebar UI to show custom label which is set on the EmbedConfig

[emilyhu0106]

@jwalgran Just for clarification - do we need to update the placeholder for the input here accordingly?

[jwalgran]

Yes. We do want to change the placeholder text.