🎨 Refactor cib library

Problem:
- The dependency DAG between `cib` sub libraries is not well-defined.

Solution:
- Define it. Each library "level" depends on the level below.

Level 0 libraries:
- `async`
- `conc`
- `fmt`
- `stdx`

Level 1 libraries:
- `cib_lookup` depends on `stdx`
- `cib_nexus` depends on `stdx`
- `cib_sc` depends on `fmt`, `stdx`

Level 2 libraries:
- `cib_log` depends on `cib_sc`
- `cib_match` depends on `cib_sc`
- `cib_interrupt` depends on `conc`, `cib_sc`

Level 3 libraries:
- `cib_flow` depends on `cib_log`, `cib_nexus`, `cib_sc`
- `cib_log_fmt` depends on `cib_log`
- `cib_msg` depends on `cib_log`, `cib_lookup`, `cib_match`, `cib_sc`

Level 4 libraries:
- `cib_log_mipi` depends on `conc`, `cib_log`, `cib_msg`
- `cib_seq` depends on `cib_flow`, `cib_log`, `cib_nexus`, `cib_sc`

Level 5 libraries:
- `cib` depends on `cib_*`

Note:
- No code has moved, so includes remain valid. `cib` remains as an omnibus library. But this paves the
  way (if we want) to move code around and separate the libraries more.

Author: elbeno

CMakeLists.txt

@@ -203,28 +203,14 @@ target_sources(
               include/log/catalog/catalog.hpp
               include/log/catalog/mipi_encoder.hpp)
 
-add_library(cib INTERFACE)
-target_compile_features(cib INTERFACE cxx_std_20)
-target_link_libraries_system(
-    cib
-    INTERFACE
-    async
-    cib_interrupt
-    cib_log
-    cib_log_fmt
-    cib_log_mipi
-    cib_lookup
-    cib_match
-    cib_msg
-    cib_sc
-    concurrency
-    fmt::fmt-header-only
-    stdx)
+add_library(cib_nexus INTERFACE)
+target_compile_features(cib_nexus INTERFACE cxx_std_20)
+target_link_libraries_system(cib_nexus INTERFACE stdx)
 
 target_sources(
-    cib
+    cib_nexus
     INTERFACE FILE_SET
-              cib
+              nexus
               TYPE
               HEADERS
               BASE_DIRS
@@ -233,7 +219,6 @@ target_sources(
               include/cib/builder_meta.hpp
               include/cib/built.hpp
               include/cib/callback.hpp
-              include/cib/cib.hpp
               include/cib/config.hpp
               include/cib/detail/components.hpp
               include/cib/detail/constexpr_conditional.hpp
@@ -244,11 +229,14 @@ target_sources(
               include/cib/detail/extend.hpp
               include/cib/detail/nexus_details.hpp
               include/cib/func_decl.hpp
-              include/cib/nexus.hpp
-              include/cib/top.hpp)
+              include/cib/nexus.hpp)
+
+add_library(cib_flow INTERFACE)
+target_compile_features(cib_flow INTERFACE cxx_std_20)
+target_link_libraries_system(cib_flow INTERFACE cib_log cib_nexus cib_sc stdx)
 
 target_sources(
-    cib
+    cib_flow
     INTERFACE FILE_SET
               flow
               TYPE
@@ -268,8 +256,19 @@ target_sources(
               include/flow/run.hpp
               include/flow/step.hpp)
 
+add_library(cib_seq INTERFACE)
+target_compile_features(cib_seq INTERFACE cxx_std_20)
+target_link_libraries_system(
+    cib_seq
+    INTERFACE
+    cib_flow
+    cib_log
+    cib_nexus
+    cib_sc
+    stdx)
+
 target_sources(
-    cib
+    cib_seq
     INTERFACE FILE_SET
               seq
               TYPE
@@ -281,6 +280,39 @@ target_sources(
               include/seq/impl.hpp
               include/seq/step.hpp)
 
+add_library(cib INTERFACE)
+target_compile_features(cib INTERFACE cxx_std_20)
+target_link_libraries_system(
+    cib
+    INTERFACE
+    async
+    cib_flow
+    cib_interrupt
+    cib_log
+    cib_log_fmt
+    cib_log_mipi
+    cib_lookup
+    cib_match
+    cib_msg
+    cib_nexus
+    cib_sc
+    cib_seq
+    concurrency
+    fmt::fmt-header-only
+    stdx)
+
+target_sources(
+    cib
+    INTERFACE FILE_SET
+              cib
+              TYPE
+              HEADERS
+              BASE_DIRS
+              include
+              FILES
+              include/cib/cib.hpp
+              include/cib/top.hpp)
+
 if(PROJECT_IS_TOP_LEVEL)
     add_docs(docs)
     clang_tidy_interface(cib)