Add overflow in contour path extraction, reported by fuzzer

[drott]

Spun off from:
https://issues.oss-fuzz.com/issues/382732980

Interesting part of stack trace:

#15 0x562cf15b2c82 in core::panicking::panic_fmt::h43c6bf7b4f5c72c3 /rustc/5315cbe15b79533f380bbb6685aa5480d5ff4ef5/library/core/src/panicking.rs:74:14
    #16 0x562cf15b3516 in core::panicking::panic_const::panic_const_add_overflow::hcdf3472a16af79c6 /rustc/5315cbe15b79533f380bbb6685aa5480d5ff4ef5/library/core/src/panicking.rs:181:21
    #17 0x562cf16f9667 in skrifa::outline::path::contour_to_path::h854d46b840da9c41 [fontations/skrifa/src/outline/path.rs:0](https://github.com/googlefonts/fontations/blob/a5bc98f8f3af8fbaaa12ae5f32228cdc684e676e/skrifa/src/outline/path.rs#L0)
    #18 0x562cf16fc57e in skrifa::outline::path::to_path::h9a8d9f122054ad00 [fontations/skrifa/src/outline/path.rs:92](https://github.com/googlefonts/fontations/blob/a5bc98f8f3af8fbaaa12ae5f32228cdc684e676e/skrifa/src/outline/path.rs#L92):9
    #19 0x562cf16f58ed in skrifa::outline::glyf::outline::ScaledOutline$LT$C$GT$::to_path::hba829ffbf6e6d9bb [fontations/skrifa/src/outline/glyf/outline.rs:158](https://github.com/googlefonts/fontations/blob/a5bc98f8f3af8fbaaa12ae5f32228cdc684e676e/skrifa/src/outline/glyf/outline.rs#L158):9
    #20 0x562cf16f58ed in skrifa::outline::hint::HintingInstance::draw::_$u7b$$u7b$closure$u7d$$u7d$::h3c382027f6b258c9 [fontations/skrifa/src/outline/hint.rs:430](https://github.com/googlefonts/fontations/blob/a5bc98f8f3af8fbaaa12ae5f32228cdc684e676e/skrifa/src/outline/hint.rs#L430):36

[drott]

@dfrg Could you take a look, this one seems to still reproduce in fuzzing.

[dfrg]

Will do. I’ll try to knock out all of the outstanding fuzzing aborts this week.