[lld][Webassembly] Avoid a signed overflow on large sections (#178287)

wasm sections sizes are specified as u32s, and thus can be as large as
4GB. wasm-ld currently stores the offset into a section as an int32_t
which overflows on large sections and results in a crash. This change
makes it a int64_t to accommodate any valid wasm section and allow
catching even larger sections instead of wrapping around.

This PR fixes the issue by storing the offset as a int64_t, as well as
adding extra checks to handle un-encodeable sections to fail instead of
producing garbage wasm binaries, and also adds lit tests to make sure it
works. I confirmed the test fails on `main` but passes with this fix.

Fixes: #178286
GitOrigin-RevId: c703f5a1632973dd6eade473614dfbed1b088d9e