Name the Value conversion functions more clearly (#11851)

# Description
This PR renames the conversion functions on `Value` to be more consistent.
It follows the Rust [API guidelines](https://rust-lang.github.io/api-guidelines/naming.html#ad-hoc-conversions-follow-as_-to_-into_-conventions-c-conv) for ad-hoc conversions.
The conversion functions on `Value` now come in a few forms:
- `coerce_{type}` takes a `&Value` and attempts to convert the value to
`type` (e.g., `i64` are converted to `f64`). This is the old behavior of
some of the `as_{type}` functions -- these functions have simply been
renamed to better reflect what they do.
- The new `as_{type}` functions take a `&Value` and returns an `Ok`
result only if the value is of `type` (no conversion is attempted). The
returned value will be borrowed if `type` is non-`Copy`, otherwise an
owned value is returned.
- `into_{type}` exists for non-`Copy` types, but otherwise does not
attempt conversion just like `as_type`. It takes an owned `Value` and
always returns an owned result.
- `coerce_into_{type}` has the same relationship with `coerce_{type}` as
`into_{type}` does with `as_{type}`.
- `to_{kind}_string`: conversion to different string formats (debug,
abbreviated, etc.). Only two of the old string conversion functions were
removed, the rest have been renamed only.
- `to_{type}`: other conversion functions. Currently, only `to_path`
exists. (And `to_string` through `Display`.)

This table summaries the above:
| Form | Cost | Input Ownership | Output Ownership | Converts `Value`
case/`type` |
| ---------------------------- | ----- | --------------- |
---------------- | -------- |
| `as_{type}` | Cheap | Borrowed | Borrowed/Owned | No |
| `into_{type}` | Cheap | Owned | Owned | No |
| `coerce_{type}` | Cheap | Borrowed | Borrowed/Owned | Yes |
| `coerce_into_{type}` | Cheap | Owned | Owned | Yes |
| `to_{kind}_string` | Expensive | Borrowed | Owned | Yes |
| `to_{type}` | Expensive | Borrowed | Owned | Yes |

# User-Facing Changes
Breaking API change for `Value` in `nu-protocol` which is exposed as
part of the plugin API.

crates/nu-explore/src/commands/expand.rs

@@ -85,7 +85,7 @@ fn convert_value_to_string(value: Value, engine_state: &EngineState, stack: &mut
     let has_single_value = vals.len() == 1 && vals[0].len() == 1;
     if !has_no_head && has_single_value {
         let config = engine_state.get_config();
-        vals[0][0].into_abbreviated_string(config)
+        vals[0][0].to_abbreviated_string(config)
     } else {
         let ctrlc = engine_state.ctrlc.clone();
         let config = engine_state.get_config();

crates/nu-explore/src/commands/nu.rs

@@ -86,7 +86,7 @@ impl ViewCommand for NuCmd {
         let (columns, values) = collect_pipeline(pipeline);
 
         if let Some(value) = has_simple_value(&values) {
-            let text = value.into_abbreviated_string(&engine_state.config);
+            let text = value.to_abbreviated_string(&engine_state.config);
             return Ok(NuView::Preview(Preview::new(&text)));
         }
 

crates/nu-explore/src/lib.rs

@@ -50,7 +50,7 @@ fn run_pager(
     p.show_message("For help type :help");
 
     if let Some(value) = has_simple_value(&data) {
-        let text = value.into_abbreviated_string(config.nu_config);
+        let text = value.to_abbreviated_string(config.nu_config);
         let view = Some(Page::new(Preview::new(&text), true));
         return p.run(engine_state, stack, ctrlc, view, commands);
     }

crates/nu-explore/src/pager/mod.rs

@@ -1008,7 +1008,7 @@ fn cmd_input_key_event(buf: &mut CommandBuf, key: &KeyEvent) -> bool {
 }
 
 fn value_as_style(style: &mut nu_ansi_term::Style, value: &Value) -> bool {
-    match value.as_string() {
+    match value.coerce_string() {
         Ok(s) => {
             *style = lookup_ansi_color_style(&s);
             true

crates/nu-explore/src/views/record/mod.rs

@@ -331,7 +331,7 @@ impl View for RecordView<'_> {
         if let Some(hm) = cfg.config.get("table").and_then(create_map) {
             self.theme = theme_from_config(&hm);
 
-            if let Some(orientation) = hm.get("orientation").and_then(|v| v.as_string().ok()) {
+            if let Some(orientation) = hm.get("orientation").and_then(|v| v.coerce_string().ok()) {
                 let orientation = match orientation.as_str() {
                     "left" => Some(Orientation::Left),
                     "top" => Some(Orientation::Top),
@@ -648,7 +648,7 @@ fn convert_records_to_string(
         .map(|row| {
             row.iter()
                 .map(|value| {
-                    let text = value.clone().into_abbreviated_string(cfg);
+                    let text = value.clone().to_abbreviated_string(cfg);
                     let float_precision = cfg.float_precision as usize;
 
                     make_styled_string(style_computer, text, Some(value), float_precision)
@@ -857,7 +857,7 @@ fn config_get_bool(config: &ConfigMap, key: &str, default: bool) -> bool {
 fn config_get_usize(config: &ConfigMap, key: &str, default: usize) -> usize {
     config
         .get(key)
-        .and_then(|v| v.as_string().ok())
+        .and_then(|v| v.coerce_string().ok())
         .and_then(|s| s.parse::<usize>().ok())
         .unwrap_or(default)
 }