[Tests] `nvm_alias`, `nvm_resolve_alias`: add edge-case tests
nvm_alias() used a sed/awk pipeline to strip comments and blank lines from alias files that almost always contain a single word.
A while-read loop with parameter expansion does the same filtering more directly.
nvm_resolve_alias() piped nvm_alias through head and tail to extract one line, and used printf/grep for cycle detection.
Parameter expansion and a case statement replace both without the extra plumbing.
All replacements are POSIX (read -r, case, IFS=, parameter expansion).
As a side effect, this also removes 4 external process invocations during shell init.
[Fix] `nvm_resolve_alias`: detect cycles via newline-anchored `case`
The original commit referenced above changed SEEN_ALIASES from `\n`-delimited
storage (interpreted by `printf '%b' | nvm_grep -e "^${name}$"`) to space-
delimited but left the line-anchored grep in place — without newlines in
the haystack the anchored pattern can never match, so cycles never break.
Switch to literal-newline storage and a `case` pattern anchored on those
newlines. Newline anchoring also handles alias names containing spaces,
which token-based patterns false-positive on (e.g. lookup of `bar` matches
substring " bar " inside " foo bar midway " when the chain visits the
multi-token alias `foo bar`).
New test file covers self-loop, multi-hop loop, cycle through a
space-bearing alias name, and a non-cycle through a space-bearing
alias name. Existing `test/fast/Aliases/circular/` fixtures continue
to pass.
