EDSC-3064: Fix 508 compliance 'Empty button' findings

[mreese84]

Please review Contribution.md before contributing to this project.

Description

Path	Finding	Location	Element
/search	Empty button	Date/time filter button	<button aria-haspopup="true" aria-expanded="false" id="temporal-selection-dropdown" type="button" class="search-form_button search-form_button--dark dropdown-toggle btn btn-inline-block"><i class="fa fa-calendar">
/search	Empty button	Spatial filter button	<button aria-haspopup="true" aria-expanded="false" id="spatial-selection-dropdown" type="button" class="search-form_button search-form_button--dark dropdown-toggle btn btn-inline-block"><i class="fa fa-crop">
/projects	Empty button	Compose button next to project name	<button type="button" class="project-header_button project-header_button--edit" label="Edit project name">
/projects	Empty button	Open/close folders for band subsetting	<button class="btn tree-item__parent-button" type="button">

Files

Acceptance Criteria

Fix 'Empty button' for all findings to be 508 compliant.