[msg] Reorder header bits to match spec.

[turon]

Problem

The SDK message header flags do not match the specification.

Change overview

In order to write tools that dissect the Matter message format, this PR attempts to align the SDK implementation with the latest specification of the message flags and security flags fields. This PR is a minimal change set. Follow on tasks include:

• encode / decode paths should handle message and security flags as separate bytes rather than as a combined, little-endian uint16
• combine kEncryptionType and kEncryptedMessage -- currently trivial attempts to do so fail PASE and MRP unit tests. The EncryptionType field is not at the proper specification location, and the kEncryptedMessage flag is a correct yet simplified view of the field.
• clean up encode/decode code paths so header processing is simplified and done in one place in all cases.

Fixes #7772. Fixes #7773. Fixes #7774.

Testing

The existing CI does a good job of validating encode / decode paths for the header flags.

[bzbarsky-apple]

/rebase

[github-actions]

Size increase report for "gn_qpg6100-example-build" from ed677f0

File	Section	File	VM
chip-qpg6100-lighting-example.out	.text	-16	-16

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

Comparing ./master_artifact/chip-qpg6100-lighting-example.out and ./pull_artifact/chip-qpg6100-lighting-example.out:

sections,vmsize,filesize
.debug_loc,0,252
.debug_str,0,16
[Unmapped],0,16
.debug_ranges,0,-16
.text,-16,-16
.debug_abbrev,0,-18
.debug_frame,0,-20
.debug_line,0,-35
.debug_info,0,-1831

Comparing ./master_artifact/chip-qpg6100-lighting-example.out.map and ./pull_artifact/chip-qpg6100-lighting-example.out.map:

BLOAT EXECUTION FAILED WITH CODE 1:
bloaty: unknown file type for file './pull_artifact/chip-qpg6100-lighting-example.out.map'

[github-actions]

Size increase report for "nrfconnect-example-build" from ed677f0

File	Section	File	VM
chip-shell.elf	text	-16	-16
chip-lock.elf	text	-16	-16

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

Comparing ./master_artifact/chip-shell.elf and ./pull_artifact/chip-shell.elf:

sections,vmsize,filesize
.debug_loc,0,233
.debug_str,0,15
.debug_ranges,0,8
.debug_frame,0,-4
.debug_line,0,-12
text,-16,-16
.debug_abbrev,0,-23
.debug_info,0,-281

Comparing ./master_artifact/chip-lock.elf and ./pull_artifact/chip-lock.elf:

sections,vmsize,filesize
.debug_loc,0,297
.debug_str,0,15
.debug_ranges,0,8
.debug_frame,0,-4
.debug_line,0,-12
text,-16,-16
.debug_abbrev,0,-23
.debug_info,0,-1777

[github-actions]

Size increase report for "esp32-example-build" from ed677f0

File	Section	File	VM
chip-all-clusters-app.elf	.flash.text	-12	-12

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

Comparing ./master_artifact/chip-pigweed-app.elf and ./pull_artifact/chip-pigweed-app.elf:

sections,vmsize,filesize

Comparing ./master_artifact/chip-all-clusters-app.elf and ./pull_artifact/chip-all-clusters-app.elf:

sections,vmsize,filesize
.debug_loc,0,54
.debug_str,0,14
.shstrtab,0,-2
.strtab,0,-10
.flash.text,-12,-12
.symtab,0,-16
.debug_abbrev,0,-18
.debug_ranges,0,-24
.debug_line,0,-26
.debug_info,0,-2192

[woody-apple]

@saurabhst @msandstedt @Damian-Nordic @jmartinez-silabs @LuDuda