Gracefully handle shutdown in worker pool

[calbera]

When shutting down an application, may see a panic like below

panic: context canceled

goroutine 1 [running]:
github.com/berachain/offchain-sdk/baseapp.(*JobManager).RunProducers(0xc00050f0b0, {0x1609860, 0xc000338ac0})
    /go/pkg/mod/github.com/berachain/offchain-sdk@v0.0.0-20240530213602-4f6189f6c32f/baseapp/job_manager.go:147 +0xb98
github.com/berachain/offchain-sdk/baseapp.(*BaseApp).Start(0xc00050f1a0, {0x1609860, 0xc000338ac0})
    /go/pkg/mod/github.com/berachain/offchain-sdk@v0.0.0-20240530213602-4f6189f6c32f/baseapp/baseapp.go:65 +0x18c
github.com/berachain/offchain-sdk/cmd.StartCmdWithOptions[...].func1({0x12eac5e, 0x4?, 0x12eab66?})
    /go/pkg/mod/github.com/berachain/offchain-sdk@v0.0.0-20240530213602-4f6189f6c32f/cmd/start.go:104 +0x504
github.com/spf13/cobra.(*Command).execute(0xc000328308, {0xc0003e4980, 0x2, 0x2})
    /go/pkg/mod/github.com/spf13/cobra@v1.8.0/command.go:983 +0xaca
github.com/spf13/cobra.(*Command).ExecuteC(0xc000328008)
    /go/pkg/mod/github.com/spf13/cobra@v1.8.0/command.go:1115 +0x3ff
github.com/spf13/cobra.(*Command).Execute(0x15f8190?)
    /go/pkg/mod/github.com/spf13/cobra@v1.8.0/command.go:1039 +0x13
main.main()
    /runner/mod/distributor/cmd/main.go:14 +0x4a

For any routines that are still ongoing, gracefully wait for completion to prevent unwanted panics.