Refactor to support multiple parse errors (#8765)

# Description

This is a pretty heavy refactor of the parser to support multiple parser
errors. It has a few issues we should address before landing:

- [x] In some cases, error quality has gotten worse `1 / "bob"` for
example
- [x] if/else isn't currently parsing correctly
- probably others

# User-Facing Changes

This may have error quality degradation as we adjust to the new error
reporting mechanism.

# Tests + Formatting

Don't forget to add tests that cover your changes.

Make sure you've run and fixed any issues with these commands:

- `cargo fmt --all -- --check` to check standard code formatting (`cargo
fmt --all` applies these changes)
- `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used -A
clippy::needless_collect` to check that you're using the standard code
style
- `cargo test --workspace` to check that all tests pass
- `cargo run -- crates/nu-utils/standard_library/tests.nu` to run the
tests for the standard library

> **Note**
> from `nushell` you can also use the `toolkit` as follows
> ```bash
> use toolkit.nu # or use an `env_change` hook to activate it
automatically
> toolkit check pr
> ```

# After Submitting

If your PR had any user-facing changes, update [the
documentation](https://github.com/nushell/nushell.github.io) after the
PR is merged, if necessary. This will help us keep the docs up to date.

crates/nu-cli/src/validation.rs

@@ -1,5 +1,8 @@
-use nu_parser::{parse, ParseError};
-use nu_protocol::engine::{EngineState, StateWorkingSet};
+use nu_parser::parse;
+use nu_protocol::{
+    engine::{EngineState, StateWorkingSet},
+    ParseError,
+};
 use reedline::{ValidationResult, Validator};
 use std::sync::Arc;
 
@@ -10,9 +13,12 @@ pub struct NuValidator {
 impl Validator for NuValidator {
     fn validate(&self, line: &str) -> ValidationResult {
         let mut working_set = StateWorkingSet::new(&self.engine_state);
-        let (_, err) = parse(&mut working_set, None, line.as_bytes(), false, &[]);
+        parse(&mut working_set, None, line.as_bytes(), false, &[]);
 
-        if matches!(err, Some(ParseError::UnexpectedEof(..))) {
+        if matches!(
+            working_set.parse_errors.first(),
+            Some(ParseError::UnexpectedEof(..))
+        ) {
             ValidationResult::Incomplete
         } else {
             ValidationResult::Complete