sheets: Client implementation assumes `Vec<Vec<String>>` but numbers are possible

The sheets crate deserializes Spreadsheet value range responses as Vec<Vec<String>>, however when using ValueRenderOption::Formula or ValueRenderOption::UnformattedValue the Google sheets API will return numbers as JSON number values.

The problem is here:

https://github.com/oxidecomputer/third-party-api-clients/blob/0861ac206f597ddc709508ef711692576b761389/google/sheets/src/lib.rs#L723

Ultimately being called from here:

https://github.com/oxidecomputer/third-party-api-clients/blob/0861ac206f597ddc709508ef711692576b761389/google/sheets/src/spreadsheets.rs#L222

Where the type Out is ValueRange which has type: Vec<Vec<String>>, but the actual JSON has number values in it. Perhaps it's a bug in the API specification?

My ugly hack is to turn them into strings, and this diff can also help visualize the problem:

https://github.com/oxidecomputer/third-party-api-clients/compare/0861ac206f597ddc709508ef711692576b761389...webern:oxide-third-party-api-clients:patch-v1?expand=1

Start in google/sheets/src/lib.rs around line 723, then follow the ValueRange use in google/sheets/src/spreadsheets.rs around line 222. Inspect how spreadsheet value range responses are deserialized for ValueRenderOption::Formula and ValueRenderOption::UnformattedValue. Done means responses containing JSON numbers deserialize successfully instead of assuming every value is a string.