This change makes debuginfo tests more user friendly. Changes:

-   Print all lines that fail to match the patterns instead of just
    the first
-   Provide better error messages that also say what did match
-   Strip leading whitespace from directives so they are not skipped if
    indented
-   Improve documentation and improve nesting on some related items

As an example, given the following debuginfo test with intentional
fails:

```rust
// from tests/debuginfo/rc_arc.rs

// cdb-command:dx rc,d
// cdb-check:rc,d             : 111 [Type: alloc::rc::Rc<i32>]
// cdb-check:    [Reference count] : 11 [Type: core::cell FAIL::Cell<usize>]
// cdb-check:    [Weak reference count] : 2 [Type: core::cell FAIL::Cell<usize>]

// ...
```

The current output (tested in rust-lang#113313) only shows the first mismatch:

```
2023-07-04T08:10:00.1939267Z ---- [debuginfo-cdb] tests\debuginfo\rc_arc.rs stdout ----
2023-07-04T08:10:00.1942182Z
2023-07-04T08:10:00.1957463Z error: line not found in debugger output:     [Reference count] : 11 [Type: core::cell FAIL::Cell<usize>]
2023-07-04T08:10:00.1958272Z status: exit code: 0
```

With this change, you are able to see all failures in that check
group, as well as what parts were successful. The output is now:

```
2023-07-04T09:45:57.2514224Z error: check directive(s) from `C:\a\rust\rust\tests\debuginfo\rc_arc.rs` not found in debugger output. errors:
2023-07-04T09:45:57.2514631Z     (rc_arc.rs:31) `    [Reference count] : 11 [Type: core::cell FAIL::Cell<usize>]`
2023-07-04T09:45:57.2514908Z     (rc_arc.rs:32) `    [Weak reference count] : 2 [Type: core::cell FAIL::Cell<usize>]`
2023-07-04T09:45:57.2515181Z     (rc_arc.rs:41) `    [Reference count] : 21 [Type: core::sync::atomic FAIL::AtomicUsize]`
2023-07-04T09:45:57.2515452Z     (rc_arc.rs:50) `dyn_rc,d         [Type: alloc::rc::Rc<dyn$<core::fmt FAIL::Debug> >]`
2023-07-04T09:45:57.2515695Z the following subset of check directive(s) was found successfully::
2023-07-04T09:45:57.2516080Z     (rc_arc.rs:30) `rc,d             : 111 [Type: alloc::rc::Rc<i32>]`
2023-07-04T09:45:57.2516312Z     (rc_arc.rs:35) `weak_rc,d        : 111 [Type: alloc::rc::Weak<i32>]`
2023-07-04T09:45:57.2516555Z     (rc_arc.rs:36) `    [Reference count] : 11 [Type: core::cell::Cell<usize>]`
2023-07-04T09:45:57.2516881Z     (rc_arc.rs:37) `    [Weak reference count] : 2 [Type: core::cell::Cell<usize>]`
...
```

Which makes it easier to see what did and didn't succeed without
manual comparison against the source test file.