Rollup merge of #34445 - pyjarrett:lang_item_table_macro_rename, r=jseyfried
Rollup merge of #34445 - pyjarrett:lang_item_table_macro_rename, r=jseyfried

Renames "lets_do_this" macro more appropriately.

The macro gets used to create a mapping of identifiers to names and their
associated functions. Since it creates a table of language items, let's rename
it in a similar manner to how vec! creates a vec.

GBGamer/rust,graydon/rust,GBGamer/rust,graydon/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,GBGamer/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,aidancully/rust