Add wasm-sdk JSON API

[yonihemi]

Add wasm-sdk JSON API

Motivation:

Missing ability to retrieve 'SDK for WebAssembly' toolchains list programmatically, like Static SDK list and platform toolchains.

Modifications:

• Added wasm-sdk API to OpenAPI spec.
• Added optional checksum property for DevToolchainForArch objects.
• Added JSON populated from yaml data for branch 6.2 and main, plus empty results for 6.0, 6.1 branches.
• Added test case to API test tool.

Result:

• Valid JSON returned from /api/v1/install/dev/<branch>/wasm-sdk.json
• Local API test passes (and with changes from Fix static-sdk JSON 6.2 API #1104, also tests branches 6.1 and 6.2)