[UI] Add Stratification Data Tab and Upload Button to Participants Content View

[danoswaltCL]

User Story
As a user, I want a view in the UI where I can manage stratified-sampling settings.

(🟠 Link to design when ready)

Dependencies:
#958

Links*
Figma Screen Recording
https://carnegielearning.slack.com/files/U02DS8JDP0Q/F05NH1DS0EP/screen_recording_2023-08-18_at_1.28.54_pm.mov

Acceptance Criteria
GIVEN I'm an experimenter,
WHEN I can click on Participant's tab in sidebar navigation
THEN I will see a tab to the right of "Participants" that says "Stratifications"
AND when I click on this tab, I will see the content page as visualized in design doc
AND I will see a an upload csv button "+ IMPORT"

GIVEN No stratification data exists in the database
THEN The content should show a 'blank' state - the content page as visualized in design doc, with an empty, headings-only table

Notes
This is intended as a UI-only task for positioning elements. Adding table and Upload button functionality will be handled in other tasks.

[zackcl]

QA: Passed