Introduce explicit type QueryLanguage = string and update code to clarify

Previously:
- There is confusion between nameWithOwner and queryLanguage.  Both are strings.
  Between

        runResult, err := codeql.RunQuery(databasePath, job.QueryLanguage, queryPackPath, tempDir)
    (agent.go l205)

  and

        func RunQuery(database string, nwo string, queryPackPath string, tempDir string) (*RunQueryResult, error)

  QueryLanguage is suddenly name with owner in the code.

  Added some debugging, the value is the query language in the two places it gets used:

        server         | 2024/07/03 18:30:15 DEBUG Processed request info location="{Data:map[bucket:packs key:1]}" language=cpp
        ...
        agent          | 2024/07/03 18:30:15 DEBUG XX: is nwo a name/owner, or the original callers' queryLanguage? nwo=cpp
        ...
        agent          | 2024/07/03 18:30:19 DEBUG XX: 2: is nwo a name/owner, or the original callers' queryLanguage? nwo=cpp

Changes:
- Introduce explicit type QueryLanguage = string and update code to clarify
- inline trivial function

pkg/server/types.go

@@ -11,7 +11,7 @@ import (
 type SessionInfo struct {
 	ID                  int
 	QueryPack           string
-	Language            string
+	Language            queue.QueryLanguage
 	AccessMismatchRepos []common.NameWithOwner
 	NotFoundRepos       []common.NameWithOwner
 	NoCodeqlDBRepos     []common.NameWithOwner