Rework log streaming and related functions (#1802)

closes #1801
closes #1815 
closes #1144
closes  #983
closes  #557
closes #1827
regression of #1791

# TODO
- [x] adjust log model
- [x] add migration for logs
- [x] send log line via grpc using step-id
- [x] save log-line to db
- [x] stream log-lines to UI
- [x] use less structs for log-data
- [x] make web UI work
  - [x] display logs loaded from db
  - [x] display streaming logs
- [ ] ~~make migration work~~ -> dedicated pull (#1828)

# TESTED
- [x] new logs are stored in database
- [x] log retrieval via cli (of new logs) works
- [x] log streaming works (tested via curl & webui)
- [x] log retrieval via web (of new logs) works

---------

Co-authored-by: 6543 <6543@obermui.de>

server/model/step_test.go

@@ -23,6 +23,7 @@ import (
 func TestTree(t *testing.T) {
 	steps := []*Step{{
 		ID:         25,
+		UUID:       "f80df0bb-77a7-4964-9412-2e1049872d57",
 		PID:        2,
 		PipelineID: 6,
 		PPID:       1,
@@ -32,6 +33,7 @@ func TestTree(t *testing.T) {
 		Error:      "0",
 	}, {
 		ID:         24,
+		UUID:       "c19b49c5-990d-4722-ba9c-1c4fe9db1f91",
 		PipelineID: 6,
 		PID:        1,
 		PPID:       0,
@@ -41,6 +43,7 @@ func TestTree(t *testing.T) {
 		Error:      "1",
 	}, {
 		ID:         26,
+		UUID:       "4380146f-c0ff-4482-8107-c90937d1faba",
 		PipelineID: 6,
 		PID:        3,
 		PPID:       1,
@@ -56,6 +59,7 @@ func TestTree(t *testing.T) {
 
 	steps = []*Step{{
 		ID:         25,
+		UUID:       "f80df0bb-77a7-4964-9412-2e1049872d57",
 		PID:        2,
 		PipelineID: 6,
 		PPID:       1,