Add `getAll` action and `SalesTaxItem`

I can split these into separate PRs if preferable.  While adding `SalesTaxItem` I realized I needed `getAll` since `SalesTaxItem` doesn't support search.

https://system.netsuite.com/help/helpcenter/en_US/Output/Help/SuiteCloudCustomizationScriptingWebServices/SuiteTalkWebServices/SalesTaxItem.html