Namadillo: Speed up Shielded-sync by adapting block bundle size to height

[Rigorously]

It takes about 12 seconds to shielded-sync from height 0 to 140,000 in the CLI, and about 1.5 minute in Namadillo, both using the MASP indexer with HTTP/2 enabled.

To reduce web worker serialization overhead, Namadillo requests blocks in bundles of 30, which adds up to 5800 bundles at this height.

To speed up shielded-sync, the block bundle size could dynamically adapt to the height difference, to switch to bundles of for example 10,000, 1,000 and 30 blocks.