Pull secrets from environment when running locally

[thomasjpfan]

Why are the changes needed?

When running locally, it is not natural to have a _FSEC_ prefix on your secrets.

What changes were proposed in this pull request?

With this PR, the _FSPEC_ prefix is not used anymore for local execution.

How was this patch tested?

I added unit tests to this PR to check the new behavior and ran this test:

from flytekit import task, Secret
from flytekit import current_context


@task(
    secret_requests=[Secret(key="apikey", group="mygroup")],
    container_image="localhost:30000/flytekit:dev",
)
def check_secret() -> str:
    ctx = current_context()
    secret = ctx.secrets.get(key="apikey", group="mygroup")
    return secret

export MYGROUP_APIKEY=my-secret
pyflyte run --remote main.py check_secret

Setup process

Screenshots

Check all the applicable boxes

• I updated the documentation accordingly.
• All new and existing tests passed.
• All commits are signed-off.

[pmahindrakar-oss]

could we convert this to utility function as i think it could be useful in other places to know if you are in local mode or not . But don't we have --remote flag that we can use to determine the same