[RFC007] Add a builder module for the new AST (#2085)

* Add bytecode::ast::builder module

This commit copies `term::make::builder` to `bytecode::ast::builder` and
change it to make it support building fields and records for the new
AST.

* Update core/src/bytecode/ast/builder.rs

* Update core/src/bytecode/ast/builder.rs

* Apply suggestions from code review

Co-authored-by: jneem <[email protected]>

* Merge some set_xxx() with xxx()

* Fix ast::builder documentation Rust example

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Co-authored-by: jneem <[email protected]>