Drop global DocList, attach the parsed result to Mailbox

[shadofren]

Drop the global DocList cache and attach DocList to Mailbox

• What does this PR do?
  Before this change, help.c contains a global DocList containing parsed Email. As help documents are parsed only once. Caching is not necessary. Thus removing all caching logic and attach the DocList to Mailbox's mdata.

• Screenshots (if relevant)

• Does this PR meet the acceptance criteria? (This is just a reminder for you,
  this section can be removed if you fulfill it.)

  • Documentation created/updated (you have to edit
    doc/manual.xml.head
    for that)

  • All builds and tests are passing

  • Added doxygen code documentation
    syntax

  • Code follows the style guide

• What are the relevant issue numbers?

[shadofren]

Hi,
I'm still having a hard time attaching doclist_free into mailbox's free_mdata.

Line 716: // m->free_mdata = help_doclist_free;

Thread 1 "neomutt" received signal SIGSEGV, Segmentation fault.
0x000055555562746d in mutt_addrlist_clear (al=0x1400000014) at address/address.c:1353
1353      if (!al)
#0  0x000055555562746d in mutt_addrlist_clear (al=0x1400000014) at address/address.c:1353
#1  0x000055555561e50e in mutt_env_free (p=p@entry=0x55555578d828) at email/envelope.c:67
#2  0x000055555561f632 in email_free (ptr=ptr@entry=0x7fffffffcd00) at email/email.c:51
#3  0x0000555555606d43 in help_doc_free (item=<optimized out>) at help/help.c:118
#4  0x000055555560849f in vector_free (v=v@entry=0x7fffffffcd40, item_free=item_free@entry=0x555555606d20 <help_doc_free>) at help/vector.c:48
#5  0x0000555555606df4 in help_doclist_free (data=<optimized out>) at help/help.c:131
#6  0x0000555555617f81 in mailbox_free (ptr=0x5555557532f0) at core/mailbox.c:64
#7  0x0000555555617dee in account_mailbox_remove (a=a@entry=0x555555753240, m=m@entry=0x0) at core/account.c:98
#8  0x0000555555617e9f in account_free (ptr=ptr@entry=0x7fffffffcdf8) at core/account.c:123
#9  0x0000555555618440 in neomutt_account_remove (n=n@entry=0x5555556c1910, a=a@entry=0x0) at core/neomutt.c:119
#10 0x00005555556184c1 in neomutt_free (ptr=0x555555689800 <NeoMutt>) at core/neomutt.c:70
#11 0x000055555556c14b in main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>) at main.c:1270

I'm not sure what happens here. Please help

[flatcap]

I think I see the problem.
The DocList and the Mailbox are sharing one array and they're both trying to free it.
Let me see if I can find the best way to sort this out.

[flatcap]

I've rebased, fixed the crashes and all the memory leaks.
Only some of the problems were yours, others you inherited (I've doc'd them all).

The main problem was the ownership of the array of Emails.
Now we clearly hand over control to the Mailbox.