add API server benchmark with lower max inflight

[anson627]

This pull request includes several changes to the pipelines/perf-eval/API Server Benchmark YAML files to update stage names, remove sku_tier parameters, and modify benchmark command arguments. The most important changes are summarized below:

Stage Name Updates:

• Changed stage names from azure_eastus2_free to azure_eastus2_default, azure_eastus2_standard to azure_eastus2_lower_max_inflight, and azure_eastus2_l7_json to azure_eastus2_l4_MI50 in apiserver-benchmark-virtualnodes10-pods100.yml and apiserver-benchmark-virtualnodes100-pods10k.yml. [1] [2] [3]

Parameter Removals:

• Removed sku_tier parameters from the workload-low and exempt sections in apiserver-benchmark-virtualnodes10-pods100.yml. [1] [2]

Benchmark Command Modifications:

• Updated benchmark command arguments by removing the --content-type parameter in apiserver-benchmark-virtualnodes100-pods10k.yml. [1] [2]

Additional Stage Configuration:

• Added a new stage azure_eastus2_default with specific variables and job parameters in apiserver-benchmark-virtualnodes100-pods3k.yml.