Ads region on iOS is unsupported if users Calendar is set to a non-default option

[kylehickinson]

Ref brave/brave-browser#7029
Relevant PR: brave/brave-core#4069

In iOS we use NSLocale to determine the users current locale and feed this into the ads library. If an iOS user sets a non-default calendar for their region (For example switching from Gregorian to Japanese) the identifier reported by NSLocale ends up looking like this en_US@calendar=japanese which then is not parsed correctly by bat-native-ads since it is looking for en_US/en-US specifically.

This results in the user seeing "Ads region not supported" status on the Rewards Settings page even if they are in a supported region

[srirambv]

Verification passed on iPhone XR with iOS 13.3.1 running 1.14.3(20.01.23.16)

• Verified changing to Japanese Calendar doesn't cause any issue with rewards
• Verified setting to Japanese Calendar and enabling rewards via onboarding works fine
• Verified setting to Japanese Calendar and enabling rewards via panel works fine
• Verified changing to Japanese calendar after rewards is enabled doesn't cause any crash

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Verification passed on iPhone 7+ with iOS 13.3.1 running 1.14.3(20.01.23.16)

• Verified changing to Japanese Calendar doesn't cause any issue with rewards
• Verified setting to Japanese Calendar and enabling rewards via onboarding works fine
• Verified setting to Japanese Calendar and enabling rewards via panel works fine
• Verified changing to Japanese calendar after rewards is enabled doesn't cause any crash

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Verification passed on iPhone 6 with iOS 12.4.4 running 1.14.3(20.01.23.16)

• Verified changing to Japanese Calendar doesn't cause any issue with rewards
• Verified setting to Japanese Calendar and enabling rewards via onboarding works fine
• Verified setting to Japanese Calendar and enabling rewards via panel works fine
• Verified changing to Japanese calendar after rewards is enabled doesn't cause any crash

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Verification passed on iPad Pro with iOS 13.3.1 running 1.14.3(20.01.23.16)

• Verified changing to Japanese Calendar doesn't cause any issue with rewards
• Verified setting to Japanese Calendar and enabling rewards via onboarding works fine
• Verified setting to Japanese Calendar and enabling rewards via panel works fine
• Verified changing to Japanese calendar after rewards is enabled doesn't cause any crash

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Verification passed on iPad Pro with iOS 12.4.4 running 1.14.3(20.01.23.16)

• Verified changing to Japanese Calendar doesn't cause any issue with rewards
• Verified setting to Japanese Calendar and enabling rewards via onboarding works fine
• Verified setting to Japanese Calendar and enabling rewards via panel works fine
• Verified changing to Japanese calendar after rewards is enabled doesn't cause any crash

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