Omit nesting_level, use indent_level to build prompt string

[tompng]

Description

The document comment says that the part %i of the prompt is indent_level.

irb/lib/irb.rb

Lines 182 to 192 in 1159c13

	# Constants +PROMPT_I+, +PROMPT_S+ and +PROMPT_C+ specify the format. In the
	# prompt specification, some special strings are available:
	#
	# %N # command name which is running
	# %m # to_s of main object (self)
	# %M # inspect of main object (self)
	# %l # type of string(", ', /, ]), `]' is inner %w[...]
	# %NNi # indent level. NN is digits and means as same as printf("%NNd").
	# # It can be omitted
	# %NNn # line number.
	# %% # %

This pull request removes calculation of nesting_level introduced in #500 and #515 and use indent_level for building prompt string.

Concerns

In test_ruby_lex.rb, the word nesting_level is used instead of indent_level.

But if we want nesting_level in prompt string again, we can easily re-implement it like this

NESTING_LEVEL_COUNTING_TOKENS = %i[on_kw on_tlambda on_tlambeg on_lparen on_lbracket on_lbrace]
def calc_nesting_level(opens)
  opens.count do |t|
    NESTING_LEVEL_COUNTING_TOKENS.include?(t.event)
  end
end

[st0012]

Looking at the commit that introduced Row, the assertion used RubyLex's @indent ivar but calling it assert_nesting_level.

Given that the same test also already had assert_indenting to check the output with indentation added, my guess is that it's just indent and nesting were somehow used interchangeably. And nesting_level was picked to avoid having both assert_indent and assert_indenting, which would be confusing.