Intercept subscribe.adblockplus.org links

[adbuker]

related to AdguardTeam/AdguardForWindows#2517
Now we have the custom URL protocol adguard:subscribe used in order to install new filter subscription (e.g. adguard:subscribe?location=...). The syntax is quite similar to the apb's custom protocol.
The detailed work scheme described in the related win's PR

[ameshkov]

Currently, it's partly implemented in #2918

However, it does not intercept subscribe.adblockplus.org links:
#2918 (comment)

Part of this logic is on the CoreLibs side -- it replaces subscribe.adblockplus.org with adguard:subscribe

[admitrevskiy]

Done (v3.3)

Testing instructions for QA:
-Reinstall AG
-Don't enable protection
-Go to https://adblockplus.org/subscriptions
-Tap on any subscription link

Expected result:
-Same as #2918 (comment)