Existing `/mcp` endpoint of Toolbox does not support auth (authorized
invocation and authenticated parameters). This PR add support for
Toolbox auth to the `/mcp` endpoint.
Added integration test for MCP with auth.
Note that Toolbox auth is **NOT** supported in stdio transport protocol,
invocations of tools with auth will result in error.
Add options for `RunToolInvokeTest()`, `RunMCPToolCallMethod()`,
`RunExecuteSqlToolInvokeTest()`.
When I was trying to update integration test for Firebird. They have a
different syntax from the usual `SELECT 1` that the other DBs are using.
If we want to update the `SELECT 1` statement in the test cases, we will
have to add a new argument and update all the other integration tests.
With `Options`, we can just add customization without having the need to
update all other integration tests. This allow the integration tests to
be more flexible. With this, we can also remove the
`GetNonSpannerWant()` since those can be set as default values for the
`Options`.
