Add icelandic g2p

[G-Thor]

This pull request adds an optional icelandic g2p, installable via tools/installers/install_ice_g2p.sh
Information and code for the g2p system can be found here and here.

This g2p is used for phonemization in my recipe for the Talromur Icelandic TTS corpus, which is in a separate pull request.

[kan-bayashi]

Thank you for your contribution!
Could you fix CI and add unit test? Just extending this part:

espnet/test/espnet2/text/test_phoneme_tokenizer.py

Lines 65 to 68 in 047d0c4

	def test_text2tokens(phoneme_tokenizer: PhonemeTokenizer):
	if phoneme_tokenizer.g2p_type is None:
	input = "HH AH0 L OW1 W ER1 L D"
	output = ["HH", "AH0", "L", "OW1", " ", "W", "ER1", "L", "D"]

[G-Thor]

Tests are failing for some other feature, but linter and tests are fine for my code:
=========================== short test summary info ============================
FAILED test/espnet2/asr/frontend/test_s3prl.py::test_frontend_init - ImportEr...
FAILED test/espnet2/asr/frontend/test_s3prl.py::test_frontend_output_size - K...
FAILED test/espnet2/asr/frontend/test_s3prl.py::test_frontend_backward - KeyE...

[sw005320]

@simpleoier, it seems that this error comes from s3prl.
Can you check it?

[simpleoier]

Sure. I'll take a look at it.
The major reason is because the update in the s3prl. I'll update the corresponding part in espnet and submit a PR soon.

[kan-bayashi]

@G-Thor could you merge master? CI is fixed.

[codecov]

Codecov Report

Merging #4384 (d0a08bc) into master (c9283d2) will decrease coverage by 0.01%.
The diff coverage is 23.07%.

@@            Coverage Diff             @@
##           master    #4384      +/-   ##
==========================================
- Coverage   82.58%   82.56%   -0.02%     
==========================================
  Files         469      469              
  Lines       40196    40209      +13     
==========================================
+ Hits        33194    33197       +3     
- Misses       7002     7012      +10     

Flag	Coverage Δ
test_integration_espnet1	66.58% <ø> (ø)
test_integration_espnet2	49.58% <23.07%> (-0.02%)	⬇️
test_python	69.35% <23.07%> (-0.02%)	⬇️
test_utils	23.45% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
espnet2/text/phoneme_tokenizer.py	83.39% <23.07%> (-3.19%)	⬇️

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