WIP: feat/1098 - Fetch masp params in Namadillo

[jurevans]

Resolves #1098

To support building shielded Tx, we need to provide MASP params. This PR hooks up fetching and storing of params in Namadillo.

Notes

• I move SessionKVStore into extension/src/extension as it uses the webextension-polyfill, meaning that package couldn't be used outside of the extension. Moving it here allows us to re-use IndexedDBKVStore in Namadillo
• In 1114 I did some experimenting with fetching these params in a service worker, however, to do this the right way, I'll need to set up a better dev/build pipeline with rollup.js/vite so that we can use modules during development. For now, I will incorporate this in Namadillo, then follow-up with delegating this to a background worker