[roll] Roll fuchsia [trace_manager] Fix Mapping Leak

We need to pass unmap the same size of mapping that we created with it.
Otherwise, we leak (part of) the mapping. This was especially noticeable
in streaming mode which would write many chunks during the session, each
leaking some of the mapping.

Testing:

Running a trace in streaming mode doesn't increase Populated memory. It
did before.
```
local/fuchsia3 ▶ ffx profile memory 2>/dev/null | rg -A 20 trace_manager.cm
Process name:         trace_manager.cm
Process koid:         26543
                                 Private                   Scaled                     Total
                           Committed    Populated    Committed    Populated    Committed    Populated
    Total                 524.19 KiB   524.19 KiB   725.75 KiB   725.75 KiB     6.24 MiB     6.24 MiB

    [scudo]                  216 KiB      216 KiB      216 KiB      216 KiB      216 KiB      216 KiB
    [relro]                   72 KiB       72 KiB       72 KiB       72 KiB       72 KiB       72 KiB
    [bss]                     68 KiB       68 KiB       68 KiB       68 KiB       68 KiB       68 KiB
    [data]                 64.05 KiB    64.05 KiB    64.05 KiB    64.05 KiB    64.05 KiB    64.05 KiB
    [stacks]                  56 KiB       56 KiB       56 KiB       56 KiB       56 KiB       56 KiB
    [bootfs-libraries]     26.86 KiB    26.86 KiB    27.12 KiB    27.12 KiB    53.72 KiB    53.72 KiB     (shared)
    bootfs                 13.28 KiB    13.28 KiB    13.98 KiB    13.98 KiB    26.55 KiB    26.55 KiB     (shared)
    [process-bootstrap]        8 KiB        8 KiB        8 KiB        8 KiB        8 KiB        8 KiB
    [blobs]                      0 B          0 B      148 KiB      148 KiB      296 KiB      296 KiB     (shared)
    [unnamed]                    0 B          0 B    52.08 KiB    52.08 KiB     5.34 MiB     5.34 MiB     (shared)
    vdso/stable                  0 B          0 B        314 B        314 B       35 KiB       35 KiB     (shared)
    vdso/next                    0 B          0 B        215 B        215 B    25.00 KiB    25.00 KiB     (shared)
local/fuchsia3 ▶ ffx trace start --duration 30  --categories "kernel"  --buffering-mode streaming
Tracing categories: [kernel]...
Trace completed! Copying trace from device...
Total size: 23029kB, Duration: 16.788973305s, Rate: 1371.67 kB/s
Post Processing Trace...
Results written to /usr/local/google/home/gmtr/local/fuchsia3/trace.fxt
Upload to https://ui.perfetto.dev/#!/ to view.
local/fuchsia3 ▶ ffx profile memory 2>/dev/null | rg -A 20 trace_manager.cm
Process name:         trace_manager.cm
Process koid:         26543
                                 Private                   Scaled                     Total
                           Committed    Populated    Committed    Populated    Committed    Populated
    Total                 524.19 KiB   524.19 KiB   725.75 KiB   725.75 KiB     6.24 MiB     6.24 MiB

    [scudo]                  216 KiB      216 KiB      216 KiB      216 KiB      216 KiB      216 KiB
    [relro]                   72 KiB       72 KiB       72 KiB       72 KiB       72 KiB       72 KiB
    [bss]                     68 KiB       68 KiB       68 KiB       68 KiB       68 KiB       68 KiB
    [data]                 64.05 KiB    64.05 KiB    64.05 KiB    64.05 KiB    64.05 KiB    64.05 KiB
    [stacks]                  56 KiB       56 KiB       56 KiB       56 KiB       56 KiB       56 KiB
    [bootfs-libraries]     26.86 KiB    26.86 KiB    27.12 KiB    27.12 KiB    53.72 KiB    53.72 KiB     (shared)
    bootfs                 13.28 KiB    13.28 KiB    13.98 KiB    13.98 KiB    26.55 KiB    26.55 KiB     (shared)
    [process-bootstrap]        8 KiB        8 KiB        8 KiB        8 KiB        8 KiB        8 KiB
    [blobs]                      0 B          0 B      148 KiB      148 KiB      296 KiB      296 KiB     (shared)
    [unnamed]                    0 B          0 B    52.08 KiB    52.08 KiB     5.34 MiB     5.34 MiB     (shared)
    vdso/stable                  0 B          0 B        314 B        314 B       35 KiB       35 KiB     (shared)
    vdso/next                    0 B          0 B        215 B        215 B    25.00 KiB    25.00 KiB     (shared)
```

Original-Fixed: 460677107
Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1427100
Original-Revision: 17ddabf0d14d74601a12570b956ac05bf3de9ca0
GitOrigin-RevId: 08f56ee32e8a748f02d43cbb0c0a474701df4109
Change-Id: I0a979131fbd651b545c24deecde76cd62b082cb2