[web] dispatch deleteIdentityAction

Summary:
dispatch the new action if usingCSAT bool is set to true. also refactored deleteUser method in IdentityServiceClientWrapper as an arrow function to avoid a method-unbinding error.

As in the previous diff in this stack, we're not modifying any reducers yet.

Depends on D10202

Test Plan:
tested the following scenarios:

account deletion on native with valid CSAT -> account deleted on keyserver and identity service (also saw DELETE_*_SUCCESS actions in redux devtools)
account deletion on native with invalid CSAT -> account deleted on keyserver and saw DELETE_IDENTITY_ACCOUNT_FAILED in devtools
account deletion on native while disconnected from identity service -> account deleted on keyserver and saw DELETE_IDENTITY_ACCOUNT_FAILED in devtools

Reviewers: inka, tomek, ashoat

Reviewed By: tomek, ashoat

Differential Revision: https://phab.comm.dev/D10352