…nfig key (#3203)

## Why make this change?

- #3201 
Two `LogLevel` bugs: Using the `None` LogLevel still emits some
`Information` messages (version, config path, etc.), and using
`"Default"` (capital D) as a key in `telemetry.log-level` config crashes
startup with `NotSupportedException`.

## What is this change?

**All logs follow the LogLevel configuration**
- Added more specific configuration for logs in the host level,
`Program.cs` which where outputing some logs that where not following
the LogLevel configuration from CLI and from configuration file.
- Add `DynamicLogLevelProvider` class which allows the loggers in the
host level to be updated after the RuntimeConfig is parsed and we know
the LogLevel.
- Add `StartupLogBuffer` class which saves the logs that are created
before we know the LogLevel, and sends them to their respective logger
after the RuntimeConfig is parsed.

**Case-insensitive `"Default"` key in config**
- `IsLoggerFilterValid` used `string.Equals` (ordinal), so `"Default"`
failed against the registered `"default"` filter.
- `GetConfiguredLogLevel` used `TryGetValue("default")`
(case-sensitive), silently ignoring `"Default"` keys.
- Both fixed with `StringComparison.OrdinalIgnoreCase` / LINQ
`FirstOrDefault`.

```json
// Now works — previously threw NotSupportedException
"telemetry": {
  "log-level": {
    "Default": "warning"
  }
}
```

```
# Now silent — previously emitted "Information: Microsoft.DataApiBuilder ..."
dab start --LogLevel None
```

## How was this tested?

- [ ] Integration Tests
- [x] Unit Tests
- `ValidStringLogLevelFilters`: added `"Default"` (capital D) data row
to cover the case-insensitive validation fix.

## Sample Request(s)

```bash
# Suppress all output
dab start --LogLevel None

# Config key now case-insensitive
# dab-config.json:
# "telemetry": { "log-level": { "Default": "none" } }
dab start
```

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: RubenCerna2079 <32799214+RubenCerna2079@users.noreply.github.com>
Co-authored-by: Ruben Cerna <rcernaserna@microsoft.com>
Co-authored-by: Aniruddh Munde <anmunde@microsoft.com>
Co-authored-by: Anusha Kolan <anushakolan10@gmail.com>