[Extensions] Rename RuntimeBlockedHosts to PolicyBlockedHosts

Enterprise policy allows for blocking extension access to a set of
hosts (defined by URLPatterns). In the code, these are referred to
frequently as RuntimeBlockedHosts; however, this is confusing with
the RuntimeHostPermissions feature. Instead, name the enterprise
policy-restricted hosts PolicyBlockedHosts to avoid ambiguity.

Leave the string entry in the policy the same for backwards
compatibility.

Bug: None

Change-Id: Icfa455e2912e3c05da58f0a0b0b8e53395d4e103
Reviewed-on: https://chromium-review.googlesource.com/1060526
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Reviewed-by: Karan Bhatia <karandeepb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#559160}

• chrome/browser/extensions/api/web_request/web_request_apitest.cc[diff]
• chrome/browser/extensions/content_script_apitest.cc[diff]
• chrome/browser/extensions/extension_management.cc[diff]
• chrome/browser/extensions/extension_management.h[diff]
• chrome/browser/extensions/extension_management_constants.cc[diff]
• chrome/browser/extensions/extension_management_constants.h[diff]
• chrome/browser/extensions/extension_management_internal.cc[diff]
• chrome/browser/extensions/extension_management_internal.h[diff]
• chrome/browser/extensions/extension_management_test_util.cc[diff]
• chrome/browser/extensions/extension_management_test_util.h[diff]
• chrome/browser/extensions/extension_management_unittest.cc[diff]
• chrome/browser/extensions/extension_service.cc[diff]
• chrome/browser/extensions/permissions_updater.cc[diff]
• chrome/browser/extensions/policy_handlers.cc[diff]
• extensions/browser/api/web_request/web_request_permissions.cc[diff]
• extensions/common/permissions/permissions_data.cc[diff]
• extensions/common/permissions/permissions_data.h[diff]