Expand necessary builtin macros eagerly

[CohenArthur]

The following list of macros is allowed to expand eagerly as of Rust 1.49. In our current implementation, this will mean tweaking that builtin's handler in rust-macro-builtins.cc in order to return a new fragment containing the unexpanded macro expansion. The list is as follows:

• Implement eager expansion for concat!()
• Implement eager expansion for format!() #1794
• Implement eager expansion for env!() #1795
• Implement eager expansion for option_env!() #1806
• Implement eager expansion for asm!() #1796
• Implement eager expansion for global_asm!() #1797
• Implement eager expansion for llvm_asm!() #1798
• Implement eager expansion for include_str!() #1804
• Implement eager expansion for include_bytes!() #1805
• Implement eager expansion for include!() #1865

I'll create associated issues for each of these tasks.

[CohenArthur]

Updated as most of the macros on this list did not need to be expanded eagerly :)