### Summary
This pull request adds the functionality to search for VAAs using Solana tx hashes, e.g.:
`GET /api/v1/vaas?txHash=2qnNNBQQQ152sGkQ1Rnq2Kdr48LvdN4oXwnTWyEmJqYYWFusLWxbwhpGS5KTXH1bKKx9gg9BLZMKd3g1cXiy7QMz`.
Also, the VAA objects returned by the API now have a new field `nativeTxHash`, which contains the tx hash that generated the VAA in the native format of the emitter chain.
Tracking issues: https://github.com/wormhole-foundation/wormhole-explorer/issues/212, https://github.com/wormhole-foundation/wormhole-explorer/issues/214
### Testing guidelines
Endpoints affected:
* `GET /api/v1/vaas` now supports Solana tx hashes by using the `?txHash=` query parameter. This search is limited to VAAs created by the portal token bridge.
* Some VAAs returned by the API should have a new field `nativeTxHash`. All VAAs related to the portal token bridge should have this field set.
* An internal refactoring affected pretty much all routes under `GET /api/v1/vaas*`, which should be re-tested.
* In the response of `/api/v1/global-tx/`, the field `originTx.signer` has been renamed to `originTx.from`