objspace_dump.c: Handle allocation path and line missing

	---
	 ext/objspace/objspace_dump.c | 13 +++++++++----
	 1 file changed, 9 insertions(+), 4 deletions(-)

ext/objspace iterates over the heap, but some slots in the heap are
poisoned, so we need to take care of that when running with ASAN

[Feature #17045] ObjectSpace.dump_all should allocate as little as possible in the GC heap

Up until this commit ObjectSpace.dump_all allocates two Hash because of `rb_scan_args`.

It also can allocate a `File` because of `rb_io_get_write_io`.

These allocations are problematic because `dump_all` dumps the Ruby
heap, so it should try modify as little as possible what it is
observing.

pointed out by Coverity Scan

The two main optimization are:
  - buffer writes for improved performance
  - avoid formatting functions when possible

```

|                   |compare-ruby|built-ruby|
|:------------------|-----------:|---------:|
|dump_all_string    |       1.038|   195.925|
|                   |           -|   188.77x|
|dump_all_file      |      33.453|   139.645|
|                   |           -|     4.17x|
|dump_all_dev_null  |      44.030|   278.552|
|                   |           -|     6.33x|
```

This is useful to see what a block of code allocated, e.g.

```
GC.start
GC.disable
ObjectSpace.trace_object_allocations do
  # run some code
end
gc_gen = GC.count
allocations = ObjectSpace.dump_all(output: :file, since: gc_gen)
GC.enable
GC.start
retentions = ObjectSpace.dump_all(output: :file, since: gc_gen)
```

It's possible to define methods with any name, even if the parser
doesn't support it and it can only be used with ex. send.

This fixes an issue where invalid JSON was output from ObjectSpace.dump
when a method name needed escaping.