Support personal access token in environment variable

[razor-x]

1. For SeamHttpMultiWorkspace, read SEAM_PERSONAL_ACCESS_TOKEN from env. Add test to env.test.ts. Basically identical logic to how SeamHttp handles SEAM_API_KEY
2. For SeamHttp, read both SEAM_PERSONAL_ACCESS_TOKEN and SEAM_WORKSPACE_ID. If both SEAM_PERSONAL_ACCESS_TOKEN and SEAM_API_KEY are defined in the env, throw an invalid options error.

[razor-x]

@andrii-balitskyi What do you think?