Invalid integers (eg integers that're too long) end up as error returns
on the `.value()` returned from the literal in the AST - previously we'd
unwrap this error, causing it to panic the compiler, but now we've got a
nice error variant for it (which just unwraps the underlying
std::num::ParseIntError).
Change-Id: I50c3c5ba89407d86659e20d8991b9658415f39a0
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6635
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>