var: Use 16-bit container for type

[jlucovsky]

Continuation of #12253

Issue: 6855: Match sigmatch type field in var and bit structs

Link to ticket: https://redmine.openinfosecfoundation.org/issues/6855

Describe changes:

• Increase type in flowbit, flowvar and generic var
• Ensure type, idx, and next pointers align on each struct.

Updates:

• Removed todo referencing issue from detect-engine-register.h

Provide values to any of the below to override the defaults.

• To use an LibHTP, Suricata-Verify or Suricata-Update pull request,
  link to the pull request in the respective _BRANCH variable.
• Leave unused overrides blank or remove.

SV_REPO=
SV_BRANCH=
SU_REPO=
SU_BRANCH=
LIBHTP_REPO=
LIBHTP_BRANCH=

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.23%. Comparing base (0e4faba) to head (c4ea039).
Report is 15 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff            @@
##           master   #12272    +/-   ##
========================================
  Coverage   83.22%   83.23%            
========================================
  Files         912      912            
  Lines      257311   257627   +316     
========================================
+ Hits       214154   214426   +272     
- Misses      43157    43201    +44     

Flag	Coverage Δ
fuzzcorpus	61.08% <ø> (+0.01%)	⬆️
livemode	19.40% <ø> (-0.13%)	⬇️
pcap	44.39% <ø> (+0.03%)	⬆️
suricata-verify	62.87% <ø> (+0.03%)	⬆️
unittests	59.18% <ø> (+<0.01%)	⬆️

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[victorjulien]

this grows the struct with no real benefit:

master:

struct FlowVar_ {
	uint8_t                    type;                 /*     0     1 */
	uint8_t                    datatype;             /*     1     1 */
	uint16_t                   keylen;               /*     2     2 */
	uint32_t                   idx;                  /*     4     4 */
	GenericVar *               next;                 /*     8     8 */
	union {
		FlowVarTypeStr     fv_str;               /*    16    16 */
		FlowVarTypeInt     fv_int;               /*    16     4 */
	} data;                                          /*    16    16 */
	uint8_t *                  key;                  /*    32     8 */

	/* size: 40, cachelines: 1, members: 7 */
	/* last cacheline: 40 bytes */
};

this PR:

struct FlowVar_ {
	uint16_t                   type;                 /*     0     2 */
	uint8_t                    datatype;             /*     2     1 */
	uint8_t                    pad;                  /*     3     1 */
	uint32_t                   idx;                  /*     4     4 */
	GenericVar *               next;                 /*     8     8 */
	uint16_t                   keylen;               /*    16     2 */

	/* XXX 6 bytes hole, try to pack */

	union {
		FlowVarTypeStr     fv_str;               /*    24    16 */
		FlowVarTypeInt     fv_int;               /*    24     4 */
	} data;                                          /*    24    16 */
	uint8_t *                  key;                  /*    40     8 */

	/* size: 48, cachelines: 1, members: 8 */
	/* sum members: 42, holes: 1, sum holes: 6 */
	/* last cacheline: 48 bytes */
};

[suricata-qa]

Information: QA ran without warnings.

Pipeline 23915