Make it possible to locally rename collections

I have two Google accounts, both having a “Holidays in Hungary” calendar and a “Contacts” calendar (with my contacts’ birthdays). They have the same IDs on the two accounts:

Discovering collections for pair cal_google_personal_to_local
[…]
  - "c5i68sj5edpm4rrfdchm6rreehgm6t3j81jn4rrle0n7cbj3c5m6arj4c5p2sprfdtjmop9ecdnmq@virtual" ("Contacts")
  - "cln2sq3ldpjm2sj9c5n26q3fdhkm8obp81jn4rrle0n7cbj3c5m6arj4c5p2sprfdtjmop9ecdnmq@virtual" ("Holidays in Hungary")
[…]
Discovering collections for pair cal_google_company_to_local
[…]
  - "c5i68sj5edpm4rrfdchm6rreehgm6t3j81jn4rrle0n7cbj3c5m6arj4c5p2sprfdtjmop9ecdnmq@virtual" ("Contacts")
  - "cln2sq3ldpjm2sj9c5n26q3fdhkm8obp81jn4rrle0n7cbj3c5m6arj4c5p2sprfdtjmop9ecdnmq@virtual" ("Holidays in Hungary")

I strongly suspect both have a global ID between all Google accounts.

It would be great to either

• give such calendars a different ID locally (my contacts on one account might differ from contacts on the other, so i might want to see the birthdays from both, without every sync causing a conflict), or
• ignore them (Hungarian holidays are the same regardless of the Google account i’m syncing; this use case is probably the same as the one in #590).

Currently using 0.16.8-2 from Arch repositories, which actually reports the version number 0.16.9.dev0+gb5dd092.d20200612. The problem seems to affect only Google calendar.

Start by reproducing the Google Calendar collection-discovery output described in the issue and review the related use case in issue #590. Determine whether the intended outcome is local collection IDs, ignoring selected collections, or both; done criteria are not defined beyond avoiding conflicts or duplicate holidays.