[CVV Storage Enhancement] Refactor get suggestions logic for credit card
and standalone cvc

1) Rename GetSuggestionsForCreditCards() to
GetCreditCardOrCvcFieldSuggestions()
2) Rename GetSuggestionsForVirtualCardStandaloneCvc() to
GetSuggestionsForVirtualCardStandaloneCvcField()
3) Created GetSuggestionsForCreditCards with
GetSuggestionsForCreditCards and
GetSuggestionsForVirtualCardStandaloneCvcField

Move get suggestions logic for credit card and standalone cvc related
logic from browser_autofill_manager to payments_suggestions_generator
GetSuggestionsForCreditCards

Hide GetSuggestionsForVirtualCardStandaloneCvcField exposure since we
expose GetSuggestionsForCreditCards instead, and call
GetSuggestionsForVirtualCardStandaloneCvcField inside
GetSuggestionsForCreditCards function

Bug: 356694842
Change-Id: I58ec8c04601048650661f5c92db93097cc717342
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5868481
Commit-Queue: Jiali Huang <jialihuang@google.com>
Reviewed-by: Jihad Hanna <jihadghanna@google.com>
Reviewed-by: Vinny Persky <vinnypersky@google.com>
Reviewed-by: Sujie Zhu <sujiezhu@google.com>
Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#1359193}