The existence of #1705 showed me that it's time to remove the bandaid
of a fix that was `normalizeFloatString` in #1537. This patch
introduces a proper Attoparsec parser for Scientific values that
handles the vaguaries of cross-language floating-point syntax. We
already depended on Attoparsec indirectly, so adding it as an explicit
dependency is fine.
A unit test is included, with examples taken from the tree-sitter corpora.
