[web] Add LoadingIndicator to ThreadSettingsGeneralTab Save button

Summary:
Related Linear issue here. Adds a LoadingIndicator to the Save button in ThreadSettingsGeneralTab to indicate that a change is in progress. Depends on D4105 because of the renaming of inputDisabled to threadSettingsOperationInProgress.

Before:

After:

Test Plan: Tested on Chrome/Safari and works as expected. However, since localhost/comm is faster than prod, the change can be seen less quickly in the videos. However, this diff is very similar to D3605 which works fine on prod.

Reviewers: atul, ashoat

Reviewed By: atul

Subscribers: palys-swm, Adrian

Differential Revision: https://phab.comm.dev/D4287