Express the "nested job control" idea directly

Prior to this fix, we would infer that nested jobs need job control.
Just pass that along explicitly in the job lineage.

src/exec.cpp

@@ -652,6 +652,7 @@ static proc_performer_t get_performer_for_process(process_t *p, job_t *job,
     lineage.parent_pgid = (job->pgid == INVALID_PID ? none() : maybe_t<pid_t>(job->pgid));
     lineage.block_io = io_chain;
     lineage.root_constructed = job->root_constructed;
+    lineage.root_has_job_control = job->wants_job_control();
 
     if (p->type == process_type_t::block_node) {
         const parsed_source_ref_t &source = p->block_node_source;
@@ -944,13 +945,18 @@ bool exec_job(parser_t &parser, const shared_ptr<job_t> &j, const job_lineage_t
         assert(*lineage.parent_pgid != INVALID_PID &&
                "parent pgid should be none, not INVALID_PID");
         j->pgid = *lineage.parent_pgid;
-        j->mut_flags().job_control = true;
     }
 
     pid_t pgrp = getpgrp();
     // Check to see if we should reclaim the foreground pgrp after the job finishes or stops.
     const bool reclaim_foreground_pgrp = (tcgetpgrp(STDIN_FILENO) == pgrp);
 
+    // If we are running nested inside a function or block with job control, then we need job
+    // control too.
+    if (lineage.root_has_job_control) {
+        j->mut_flags().job_control = true;
+    }
+
     if (j->pgid == INVALID_PID && should_claim_process_group_for_job(j)) {
         j->pgid = pgrp;
     }

src/parse_execution.cpp

@@ -1265,7 +1265,8 @@ end_execution_reason_t parse_execution_context_t::run_1_job(tnode_t<g::job> job_
     auto job_control_mode = get_job_control_mode();
     bool wants_job_control =
         (job_control_mode == job_control_t::all) ||
-        ((job_control_mode == job_control_t::interactive) && parser->is_interactive());
+        ((job_control_mode == job_control_t::interactive) && parser->is_interactive()) ||
+        lineage.root_has_job_control;
 
     job_t::properties_t props{};
     props.wants_terminal = wants_job_control && !ld.is_event;

src/proc.h

@@ -280,6 +280,10 @@ struct job_lineage_t {
     /// is part of a pipeline, then this may be set.
     maybe_t<pid_t> parent_pgid{};
 
+    /// Whether job control is on for the root.
+    /// This is set if our job is nested as part of a function or block execution.
+    bool root_has_job_control{false};
+
     /// The IO chain associated with any block containing this job.
     /// For example, in `begin; foo ; end < file.txt` this would have the 'file.txt' IO.
     io_chain_t block_io{};