[MOB-1109] Remove keystore from Git

[JinW-Airwallex]

This PR:

• Removed keystore file from Git. The keystore has the private upload key to sign the bundle for Play distributions. We'll need to email Google Play support with the new public upload key to change it.
• Migrated signing to Bitrise. The existing keystore is uploaded to Bitrise to sign the sample bundle. After our new keystore approved by Google, we'll update there directly.
• Migrated sample app delivery pipeline to Bitrise. This aligns with the sample iOS app.
• Used the service account's PAT for tagging for automatic release. Otherwise the maven workflow won't be triggered.

The email containing the certificate of the new keystore has been sent to Play support. The keystore has also been updated on LastPass.

[JinW-Airwallex]

We'll not remove the keystore from the Git history as that's going to be challenging. We'll simply create a new keystore so that the old one doesn't make sense anymore.

[github-actions[bot]]

Unit Test Results

234 tests  ±0   234 :heavy_check_mark: ±0   1m 18s :stopwatch: -2s   97 suites ±0       0 :zzz: ±0    97 files   ±0       0 :x: ±0 

Results for commit 5d13dd70. ± Comparison against base commit bbf0ffba.