Currently, the spans of expressions are recorded only relative to the
template node that they reside in, not their source file.
Introduce a `sourceSpan` property on expression ASTs that records the
location of an expression relative to the entire source code file that
it is in. This may allow for reducing duplication of effort in
ngtsc/typecheck/src/diagnostics later on as well.
Child of #31898
PR Close#31897
Ayaz Hafiz