Expose normalizedNumberFormat for normalized % stack

[kanitw]

For normalized stacked charts (like bar), we automatically generate tooltips that calculates ratio / %.

However, we haven't applied any % formatting to this % tooltip yet.

We should

1. Expose config.normalizedNumberFormat (or percentFormat or sth) for setting formatter for this % tooltip

• Probably also add config.normalizedNumberFormatType so this config.normalizedNumberFormat has its own format type.

2. Set the default config.normalizedNumberFormat (defaultConfig in config.ts) --- probably to.2%?

For testing, perhaps:

1. modify stacked_bar_normalize.vl.json to include tooltip: true in mark to test the default format
   and
2. add stacked_bar_normalize_custom_format.vl.json to test customized format in the config.

[kanitw]

cc: @domoritz @jheer @arvind

Any opinion for the config name?

At first I thought percentFormat/percentNumberFormat, but then the feature is only trigger via "normalize" stack and technically users don't really need to do % as the formatter, so config.normalizedNumberFormat might best match what the feature is for.

[domoritz]

I like normalizedNumberFormat.

[lsh]

Resolved by #8307