Don't split Eshell expansions by line when using split-subscript operator

* lisp/eshell/esh-var.el (eshell-apply-indices): Use
'eshell-convert-to-number' instead of 'eshell-convert'.

* test/lisp/eshell/esh-var-tests.el
(esh-var-test/interp-convert-var-split-indices): Expand test
(bug#55838).
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skipped #47045
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skipped #47044
test-lisp-inotify
skipped #47046
test-src-inotify
 
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#12 7473.   ELC      international/robin.elc
#12 7474. ELC international/textsec-check.elc
#12 7474. ELC international/textsec.elc
#12 7478. ELC international/utf-7.elc
#12 7479. ELC international/utf7.elc
#12 7480. ELC language/china-util.elc
#12 7480. ELC language/cyril-util.elc
#12 7481. ELC language/ethio-util.elc
#12 7483. ELC language/hanja-util.elc
#12 7484. ELC language/ind-util.elc