wasm: implement inline assembly

[l1mey112]

This PR implements support for inline assembly inside the wasm backend. This also allows removal of all __builtins present in the standard library, replacing them with vwasm_* functions instead, implemented with inline assembly. Compile time conditional compilation is also implemented, as well as some v fmt changes.

This PR touches the following modules:

• import wasm - Minor fixes.
• import v.gen.wasm - Implementation.
• import v.pref - wasm arch changes.
• import v.parser - Parsing wasm in asm blocks.
• import v.fmt - Proper formatting for arch string.
• import builtin - Remove wasm builtins, and replace with inline assembly.

🤖 Generated by Copilot at eb1eb54

This pull request adds support for compiling V code to WebAssembly (wasm) as a target operating system. It refactors the wasm memory management functions, improves the wasm code generation and error handling, adds support for inline assembly and comptime evaluation for wasm, and adds tests for the wasm features. It modifies the files vlib/builtin/wasm/builtin.v, vlib/v/gen/wasm/gen.v, vlib/v/parser/parser.v, vlib/v/pref/pref.v, vlib/wasm/instructions.v, and vlib/v/ast/ast.v, and adds the files vlib/builtin/wasm/alloc.v, vlib/v/gen/wasm/mem.v, vlib/v/fmt/asm.v, vlib/v/gen/wasm/comptime.v, and vlib/v/gen/wasm/tests/*.vv*.

🤖 Generated by Copilot at eb1eb54

• Split builtin.v into builtin.v and alloc.v and implement memory allocation and manipulation functions for wasm using inline assembly (link, link, link, link, link, link)
• Add wasm32 case to gen_asm method and format assembly statements with wasm literal for wasm architecture (link, link)
• Add comptime.v file and define functions for comptime evaluation of conditional expressions for wasm using $if directives (link)
• Modify v_error method to exit with code 1 instead of returning and remove unused code for output modes for wasm (link, link)
• Replace __heap_base global with hp method that returns heap base global index using wasm module and create global if needed (link, link)
• Check if if expression is comptime and call comptime_if_expr method for wasm (link)
• Add case for ast.AsmStmt and call asm_stmt method for wasm in gen_stmt method (link)
• Wrap type argument with ast.mktyp in new_global method to ensure valid type (link)
• Define tee method to copy value from stack to variable for inline assembly (link)
• Add asm.vv file and asm.vv.out file to test inline assembly feature for wasm with various arithmetic, memory, and conversion operations (link, link)
• Add tests for wasm builtins in builtin.vv file and builtin.vv.out file (link, link)
• Add comptime.vv file and comptime.vv.out file to test comptime evaluation of conditional expressions for wasm (link, link)
• Report error if assembly statement is at top level and architecture is wasm32 and add wasm as valid option in error message in parse_asm_stmt method (link, link)
• Add select and return as v keywords that are also wasm instructions and append them to instruction name in parse_asm_stmt method (link)
• Handle instruction name with dot and check if token after dot is const and append it to name in parse_asm_stmt method (link)
• Handle instruction argument as string literal and add it to argument list in parse_asm_stmt method (link)
• Report error if instruction argument is addressing operand for wasm32 architecture in parse_asm_stmt method (link)
• Add case for wasm and wasm32 in parse_target_os and os_from_str methods and set compile_defines and arch fields accordingly (link, link)
• Rename sign_extend32_i64 method to sign_extend32 to match wasm instruction name and add is_signed parameter to cast_trapping method and use different instructions depending on parameter (link, link)

[medvednikov]

Great work!