merge TCP implementations in tcp.c (#748)

Merge TCP implementations in `tcp.c` as suggested in
#745 (comment)

---------

Signed-off-by: Roman Volosatovs <rvolosatovs@riseup.net>

Author: rvolosatovs

expected/wasm32-wasip2/defined-symbols.txt

@@ -342,8 +342,6 @@ __wasilibc_rmdirat
 __wasilibc_sockaddr_to_wasi
 __wasilibc_sockaddr_validate
 __wasilibc_stat
-__wasilibc_tcp_getsockopt
-__wasilibc_tcp_setsockopt
 __wasilibc_tell
 __wasilibc_unlinkat
 __wasilibc_unspecified_addr
@@ -1346,7 +1344,6 @@ tanl
 tcp_borrow_tcp_socket
 tcp_create_socket_create_tcp_socket
 tcp_create_socket_result_own_tcp_socket_error_code_free
-tcp_getpeername
 tcp_ip_socket_address_free
 tcp_method_tcp_socket_accept
 tcp_method_tcp_socket_address_family

expected/wasm32-wasip3/defined-symbols.txt

@@ -339,8 +339,6 @@ __wasilibc_rmdirat
 __wasilibc_sockaddr_to_wasi
 __wasilibc_sockaddr_validate
 __wasilibc_stat
-__wasilibc_tcp_getsockopt
-__wasilibc_tcp_setsockopt
 __wasilibc_tell
 __wasilibc_unlinkat
 __wasilibc_unspecified_addr

libc-bottom-half/CMakeLists.txt

@@ -145,7 +145,7 @@ else()
     sources/socket.c
     sources/sockets_utils.c
     sources/sockopt.c
-    sources/tcp_sockopt.c
+    sources/tcp.c
   )
 endif()
 
@@ -156,7 +156,6 @@ if(WASI STREQUAL "p2")
     sources/wasip2_file.c
     sources/wasip2_file_utils.c
     sources/wasip2_stdio.c
-    sources/wasip2_tcp.c
     sources/wasip2_udp.c
   )
 endif()
@@ -168,7 +167,6 @@ if (WASI STREQUAL "p3")
     sources/wasip3_file.c
     sources/wasip3_file_utils.c
     sources/wasip3_stdio.c
-    sources/wasip3_tcp.c
     sources/wasip3_udp.c
   )
 endif()