Rename esp32s2 port to espressif

[tannewt]

This is in preparation for ESP32-S3 support and potentially others.

Related to #4363

[microdev1]

@tannewt Thanks for looking into this. The CI failure is due to a few xtensa and esp32s2 still around.

I have pointed out a few here but there might be more:

circuitpython/.github/workflows/build.yml

Line 21 in 973a90f

xtensa-boards: ${{ steps.set-matrix.outputs.xtensa-boards }}

circuitpython/tools/ci_changed_board_list.py

Line 86 in 973a90f

arch_to_boards = {"arm": [], "riscv": [], "xtensa": []}

circuitpython/.gitmodules

Lines 153 to 159 in 973a90f

	[submodule "ports/esp32s2/esp-idf"]
	path = ports/espressif/esp-idf
	url = https://github.com/espressif/esp-idf.git
	branch = release/v4.3
	[submodule "ports/esp32s2/certificates/nina-fw"]
	path = ports/espressif/certificates/nina-fw
	url = https://github.com/adafruit/nina-fw.git

circuitpython/.pre-commit-config.yaml

Line 11 in 973a90f

exclude: '^(tests/.*\.exp|tests/cmdline/.*|tests/.*/data/.*|ports/esp32s2/esp-idf-config/.*|ports/esp32s2/boards/.*/sdkconfig)'

[microdev1]

LGTM! 👍