dotnet-counters stops working when tag contains comma or equal sign

This is actually a dotnet/runtime problem (in my opinion), but it definitely breaks `dotnet-counters` so I figured I'd start here.

When a monitored application emits a `System.Diagnostics.Metrics` instrument whose tag values contain `,` or `=`, `dotnet-counters` displays the counter name but never renders any tag columns or values, and the display stops updating.

Although it's a bug in counters, the underlying problem in the runtime is that `MetricsEventSource` flattens the tag list for out-of-process consumers into a `key=value,key=value` string, which can't be reliably parsed if `value` contains commas or equal signs.

Minimal .NET 10 repro:

```csharp
using System.Diagnostics.Metrics;

using var meter = new Meter("TagTest");
var counter = meter.CreateCounter("hits");

Console.WriteLine($"PID: {Environment.ProcessId}");
while (true)
{
counter.Add(1,
new KeyValuePair("plain", "simple"),
new KeyValuePair("comma", "a,b,c"),
new KeyValuePair("equals", "x=1"),
new KeyValuePair("url", "/api/items?filter=red,blue&sort=name"));
Thread.Sleep(250);
}
```

The payload looks like this, and the problem is already obvious:

```
comma=a,b,c,equals=x=1,plain=simple,url=/api/items?filter=red,blue&sort=name
```

When you run `dotnet-counters monitor --process-id --counters TagTest`, instead of columns for `plain`, `comma`, `equals`, and `url`, you get:

```
[TagTest]
hits (Count)
```

...then it stops updating. I didn't dig into dotnet-counters to find _that_ problem because I had already run into the general tagging problem in my own program, and I wondered if counters had some magic to fix it. (I did actually come up with some ugly code that resolves those, but a tag like `key=a=1,b=2` where `a=1,b=2` is the value can't be resolved; definitely an edge case but still a problem.)

I suppose some kind of escaping of commas and equal signs in the key values is called for, or emit the tag list in a structured fashion (JSON, a `Dictionary`, etc). ... obviously that's up to you folks. As far as I know OTel doesn't require any particular format, so there wouldn't be a violation of any standard if this changes.

Environment:
* dotnet-counters 9.0.661903
* .NET SDK 10.0.301
* Linux x64