Add --generate-hex flag to forc build

[nedsalk]

It would be beneficial to have the option for forc build to create a hex representation of the binary, as javascript bundlers cannot bundle .bin files. The @FuelLabs/sdk-ts overcomes this by hexing the binary when running fuels typegen, a CLI tool which enables a type-safe experience when interacting with sway programs. This issue intends to remove this CLI tool's type-safety part by moving from file generation to compile-time type inference of the ABI. However, the problem of hexing binaries would still remain and we wouldn't be able to get rid of the CLI tool completely.
If forc build were to output the hexed version of the binary, it would improve the developer experience of our ts-sdk and would align it with how the rust-sdk doesn't need any CLI tool. It would also be a big step up relative to the TS ethereum ecosystem, where CLI tools are still necessary.