On UNIX, use `tee` to get the output to stdout and `grep` the stream
afterwards without using an output file.

For Windows, use powershell's `tee` equiv (`Tee-Object`) and display the
log file before grepping it.

This will surface any errors that occur alongside the failed grep exit code.

A few elements of our public API had no associated docs. This is going
to be flagged as an error by the API doc generation tooling, so let's
fix it up-front with some short doc additions.

In a subsequent commit we're adding a docgen tool to the tools crate
with a dep that requires a higher MSRV than the main crate.

To make this less painful this commit excludes the tools crate from the
workspace default list and skips usage of the ech-fetch tool for the
MSRV runs.

This commit adds a `docgen` binary to the tools crate. This tool can
generate a .json file describing the API based on parsing the `cbindgen`
generated `rustls.h` header file using a tree-sitter C grammar.

The produced JSON can in turn be used to generate markdown web
documentation, or any other format required.

Along with generating docs this tool applies some basic policy. In
particular it requires that **all** public API items be documented or it
will produce an error instead of the JSON data. We can extend this in
the future to require (for example) describing arguments and return
values in doc comments.

The generated JSON has the following structure:

```json
{
  "structs": [ .. ],
  "functions": : [ .. ],
  "callbacks": [ .. ],
  "enums": [ .. ],
  "externs": [ .. ],
  "aliases": [ .. ]
}
```

Where each key is a general category of item:

* Structure definitions
* API function prototypes
* Callback typedefs
* Enum typedefs
* Extern typedefs
* Simple type alias typdefs

Within each category items are described like:

```json
{
  "anchor": "rustls-accepted",
  "comment": "A parsed ClientHello produced by a ...",
  "name": "rustls_accepted",
  "text": "```c\nstruct rustls_accepted\n```"
},
```

The anchor field is useful for creating anchor links that identify the
item. The name is the actual name of the item. The comment is the
C block comment content (with the block comment syntax removed, but
other whitespace left as-is). Lastly the text field holds the actual
text that defines the item in rustls.h (without comment) as
a C formatted markdown code block.

This commit adds a Zola[0] website that can template the API docs JSON
data into a nice website showing off our API.

The choice of Zola (and the initial CSS/config) are inspired by the
https://rustls.dev website which also uses Zola.

To use:
```
cargo run --bin docgen > website/static/api.json
cd website && zola serve
open http://locahost:1111
```

[0]: https://www.getzola.org/

Lifted from the equivalent config in the rustls repo, and customized for
rustls-ffi.