Search: Record Meter. Replaces localStorage with sessionStorage

[annacmc]

This tiny PR switches the notice box dismissal/persistence from using localStorage to using sessionStorage

Does this pull request change what data or activity we track or use?

no

Testing instructions:

• On a site with an active Jetpack Search subscription, go to /wp-admin/admin.php?page=jetpack-search&features=record-meter and check there is currently no notice box displaying.

• toggle off/on the different states hasBeenIndexed hasValidData and 'hasItemsto trigger the different notices. Note thathasValidData` being false should resolve a red notice box instead:

toggle the states in inspector	red noticed when hasValidData is false

• Try dismissing the notice box using the 'X' in the top right corner of the notice box. It should disappear. When the window is refreshed, dismissed notice should persist. However, other notices should still be able to be displayed (until they too are dismissed)

• When the session is ended (eg. cleared, or in a different browser etc) the notices should once again display.

[github-actions]

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[bluefuton]

Test out well for me. 🚢

I notice one unrelated nit - the close icon on the notice box has the title 'Close search results' which obviously doesn't apply here! I'll fix that over in #24328.