Fix leftover from #8236 and make BufferReader/Writer support Span

[tcarmelveilleux]

Problem

• In Make ECDSA sign/verify format spec-compliant #8236, @bzbarsky-apple left several nit comments. Those need to be fix by a follow-up
• One of the core comments was to use Span rather than <uint8_t *, size_t> sets of args. To do so, it was cleaner to add Span support to Reader and BufferWriter, so I did so.

Change overview

• Fix leftover nits from @bzbarsky-apple's review of Make ECDSA sign/verify format spec-compliant #8236
• In order to add span support cleanly, added Span support to
  Reader and BufferWriter, and fixed all necessary breakage.
• Use new span function for validity checks (is_span_usable)
• Replace an untested CHIPCert.cpp usage with tested version
• Add unit tests to RawIntegerToDer

Testing

• Ran cert tests (scripts/tests/test_suite.sh) integration tests
• Ran ninja -C out/host check on Linux
• Added unit tests to cover new Reader and BufferWriter features and RawIntegerToDer

[todo]

De-uint16-ify everything related to this library

connectedhomeip/src/transport/raw/MessageHeader.cpp

Lines 147 to 150 in 672ddc0

	// TODO: De-uint16-ify everything related to this library
	uint16_t octets_read;
	uint16_t header;

---

This comment was generated by todo based on a TODO comment in 672ddc0 in #8408. cc @tcarmelveilleux.

[github-actions]

Size increase report for "esp32-example-build" from 193eb3c

File	Section	File	VM
chip-all-clusters-app.elf	.flash.text	104	104
chip-temperature-measurement-app.elf	.flash.text	112	112
chip-shell.elf	.flash.text	40	40
chip-lock-app.elf	.flash.text	84	84

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

Comparing ./master_artifact/chip-persistent-storage.elf and ./pull_artifact/chip-persistent-storage.elf:

sections,vmsize,filesize
.debug_info,0,1896
.debug_line,0,69
.debug_str,0,3

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

sections,vmsize,filesize
.debug_info,0,40969
.debug_line,0,6671
.debug_abbrev,0,514
.debug_str,0,449
.debug_loc,0,357
.flash.text,104,104
.strtab,0,98
.shstrtab,0,-2
[Unmapped],0,-104
.debug_ranges,0,-272

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

sections,vmsize,filesize
.debug_info,0,632
.debug_line,0,23
.debug_str,0,1

Comparing ./master_artifact/chip-temperature-measurement-app.elf and ./pull_artifact/chip-temperature-measurement-app.elf:

sections,vmsize,filesize
.debug_info,0,39130
.debug_line,0,5272
.debug_abbrev,0,509
.debug_str,0,448
.flash.text,112,112
.debug_loc,0,105
.strtab,0,98
.shstrtab,0,-2
[Unmapped],0,-112
.debug_ranges,0,-248

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

sections,vmsize,filesize
.debug_info,0,29196
.debug_line,0,2895
.debug_str,0,757
.debug_abbrev,0,422
.debug_loc,0,118
.flash.text,40,40
[Unmapped],0,-40
.debug_ranges,0,-184

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

sections,vmsize,filesize
.debug_info,0,42695
.debug_line,0,5760
.debug_abbrev,0,976
.debug_str,0,448
.debug_loc,0,425
.strtab,0,98
.flash.text,84,84
.shstrtab,0,-2
[Unmapped],0,-84
.debug_ranges,0,-256

[github-actions]

Size increase report for "nrfconnect-example-build" from 193eb3c

File	Section	File	VM
chip-lock.elf	text	112	112
chip-shell.elf	text	52	52
chip-shell.elf	device_handles	-4	-4

Full report output

BLOAT REPORT

Files found only in the build output:
    report.csv

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

sections,vmsize,filesize
.debug_info,0,20890
.debug_line,0,1788
.debug_abbrev,0,502
.debug_str,0,499
.debug_ranges,0,400
text,112,112
.debug_loc,0,101
.debug_frame,0,4

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

sections,vmsize,filesize
.debug_info,0,16661
.debug_line,0,1117
.debug_str,0,717
.debug_abbrev,0,386
text,52,52
.debug_frame,0,4
device_handles,-4,-4
.debug_ranges,0,-48
.debug_loc,0,-53