Previously, interpolations were generated into TCBs as a comma-separated
list of expressions, letting TypeScript infer the type of the expression
as the type of the last expression in the chain. This is undesirable, as
interpolations always result in a string type at runtime. Therefore,
type-checking of bindings such as `<img src="{{ link }}"/>` where `link`
is an object would incorrectly report a type-error.
This commit adjusts the emitted TCB code for interpolations, where a
chain of string concatenations is emitted, starting with the empty string.
This ensures that the inferred type of the interpolation is of type string.
PR Close#30177
0937062a64