Replace Distributed with Malt

- Remove `workspace_use_distributed` flag. Pluto will now always use
  separate processes.
- Replace calls to `remotecall_eval` with the appropiate Malt calls.
- Replace Distributed with Malt in tests to remove it from dependencies.
  - Add `unmake_workspace` calls in `MacroAnalysis` to prevent creating
    too many processes at the same time.
- Replace Distributed exceptions with Malt exceptions.
- Replace `pid::Integer` with `worker::Worker` in WorkspaceManager.
- Rename `workspaces` to `active_workspaces`.
- Rename `distributed_exception_result` to `workspace_exception_result`.
- Rename `make_distributed_serializable` to `make_serializable`.

Project.toml

@@ -16,13 +16,15 @@ HypertextLiteral = "ac1192a8-f4b3-4bfe-ba22-af5b92cd3ab2"
 InteractiveUtils = "b77e0a4c-d291-57a0-90e8-8db25a27a240"
 Logging = "56ddb016-857b-54e1-b83d-db4d58db5568"
 MIMEs = "6c6e2e6c-3030-632d-7369-2d6c69616d65"
+Malt = "36869731-bdee-424d-aa32-cab38c994e3b"
 Markdown = "d6f4376e-aef5-505a-96c1-9c027394607a"
 MsgPack = "99f44e22-a591-53d1-9472-aa23ef4bd671"
 Pkg = "44cfe95a-1eb2-52ea-b672-e2afdf69b78f"
 PrecompileSignatures = "91cefc8d-f054-46dc-8f8c-26e11d7c5411"
 REPL = "3fa0cd96-eef1-5676-8a61-b3b8758bbffb"
 RegistryInstances = "2792f1a3-b283-48e8-9a74-f99dce5104f3"
 RelocatableFolders = "05181044-ff0b-4ac5-8273-598c1e38db00"
+Serialization = "9e88b42a-f829-5b0c-bbe9-9e923198166b"
 Sockets = "6462fe0b-24de-5631-8697-dd941f90decc"
 TOML = "fa267f1f-6049-4f14-aa54-33bafae1ed76"
 Tables = "bd369af6-aec1-5ad0-b16a-f7cc5008161c"
@@ -35,6 +37,7 @@ FuzzyCompletions = "0.3, 0.4, 0.5"
 HTTP = "^1.0.2"
 HypertextLiteral = "0.7, 0.8, 0.9"
 MIMEs = "0.1"
+Malt = "^0.7.0"
 MsgPack = "1.1"
 PrecompileSignatures = "3"
 RegistryInstances = "0.1"

src/Configuration.jl

@@ -128,7 +128,6 @@ Note that Pluto is quickly evolving software, maintained by designers, educators
 end
 
 const RUN_NOTEBOOK_ON_LOAD_DEFAULT = true
-const WORKSPACE_USE_DISTRIBUTED_DEFAULT = true
 const LAZY_WORKSPACE_CREATION_DEFAULT = false
 const CAPTURE_STDOUT_DEFAULT = true
 const WORKSPACE_CUSTOM_STARTUP_EXPR_DEFAULT = nothing
@@ -140,14 +139,12 @@ Options to change Pluto's evaluation behaviour during internal testing and by do
 These options are not intended to be changed during normal use.
 
 - `run_notebook_on_load::Bool = $RUN_NOTEBOOK_ON_LOAD_DEFAULT` Whether to evaluate a notebook on load.
-- `workspace_use_distributed::Bool = $WORKSPACE_USE_DISTRIBUTED_DEFAULT` Whether to start notebooks in a separate process.
 - `lazy_workspace_creation::Bool = $LAZY_WORKSPACE_CREATION_DEFAULT`
 - `capture_stdout::Bool = $CAPTURE_STDOUT_DEFAULT`
 - `workspace_custom_startup_expr::Union{Nothing,Expr} = $WORKSPACE_CUSTOM_STARTUP_EXPR_DEFAULT` An expression to be evaluated in the workspace process before running notebook code.
 """
 @option mutable struct EvaluationOptions
     run_notebook_on_load::Bool = RUN_NOTEBOOK_ON_LOAD_DEFAULT
-    workspace_use_distributed::Bool = WORKSPACE_USE_DISTRIBUTED_DEFAULT
     lazy_workspace_creation::Bool = LAZY_WORKSPACE_CREATION_DEFAULT
     capture_stdout::Bool = CAPTURE_STDOUT_DEFAULT
     workspace_custom_startup_expr::Union{Nothing,Expr} = WORKSPACE_CUSTOM_STARTUP_EXPR_DEFAULT
@@ -254,7 +251,6 @@ function from_flat_kwargs(;
         require_secret_for_open_links::Bool = REQUIRE_SECRET_FOR_OPEN_LINKS_DEFAULT,
         require_secret_for_access::Bool = REQUIRE_SECRET_FOR_ACCESS_DEFAULT,
         run_notebook_on_load::Bool = RUN_NOTEBOOK_ON_LOAD_DEFAULT,
-        workspace_use_distributed::Bool = WORKSPACE_USE_DISTRIBUTED_DEFAULT,
         lazy_workspace_creation::Bool = LAZY_WORKSPACE_CREATION_DEFAULT,
         capture_stdout::Bool = CAPTURE_STDOUT_DEFAULT,
         workspace_custom_startup_expr::Union{Nothing,Expr} = WORKSPACE_CUSTOM_STARTUP_EXPR_DEFAULT,
@@ -294,7 +290,6 @@ function from_flat_kwargs(;
     )
     evaluation = EvaluationOptions(;
         run_notebook_on_load,
-        workspace_use_distributed,
         lazy_workspace_creation,
         capture_stdout,
         workspace_custom_startup_expr,