Upgrade Bifrost-polkadot to Runtime 0.15.2

Bifrost Polkadot Runtime

🏋️  Runtime size:             2.257 MB (2,366,317 bytes) ⚠️ HEAVY
🗜  Compressed:               Yes, 76.83%
✨ Reserved meta:            OK - [6D, 65, 74, 61]
🎁 Metadata version:         V14
🔥 Core version:             bifrost_polkadot-15002 (bifrost_polkadot-0.tx1.au0)
🗳️  system.setCode hash:      0x8be127d2e4360f262006a8a8f8a1f40490b8a1c6a5eb52ade5c94da263c3df19
🗳️  authorizeUpgrade hash:    0x374714730713e5b822a989aaeaae802476cc360cf2b701661dd33da0c2698342
🗳️  Blake2-256 hash:          0x10f918691ad5790833f0dca5d490c3e883a54a9f0ee1a718577fd649b82791b9
📦 IPFS:                     https://www.ipfs.io/ipfs/QmU8Da9fR9LuV6gnxYH4D72nzdT8FTxe5sd6urFMsAfK2W

What's Changed

• Separate the logic for retrieving the current block for different tok… by @SunTiebing in https://github.com/bifrost-io/bifrost/pull/1538
• Fix vtoken voting by @SunTiebing in https://github.com/bifrost-io/bifrost/pull/1540

Full Changelog: https://github.com/bifrost-io/bifrost/compare/bifrost-v0.15.1...bifrost-v0.15.2