Add vedic accent support to all Indic fonts

[vvasuki]

Following up from https://github.com/googlefonts/noto-fonts/issues/1753#issuecomment-1028617929 :

All Indic fonts ought to support all vedic accents (listed below). Currntly - some do (devanAgarI), others don't (partially or fully) - eg. shAradA.

Examples: શૂ꣢રો꣣ નૃ꣡ષા꣢તા꣣ શ્ર꣡વ꣢સશ્ચ꣣ કા꣢મ꣣ આ꣡ ગોમ꣢꣯તિ વ્ર꣣જે꣡ ભ꣢જા꣣ ત્વં꣡ નઃ꣢ ॥ 26:0318 ॥

ઇ꣢ન્દ્રં꣣ ન꣡રો꣢ ને꣣મ꣡ધિ꣢તા હવન્તે꣣ ય꣡ત્પાર્યા꣢꣯ યુ꣣ન꣡જ꣢તે꣣ ધિ꣢ય꣣સ્તાઃ꣢। શૂ꣢રો꣣ નૃ꣡ષા꣢તા꣣ શ્ર꣡વ꣢સશ્ચ꣣ કા꣢મ꣣ આ꣡ ગોમ꣢꣯તિ વ્ર꣣જે꣡ ભ꣢જા꣣ ત્વં꣡ નઃ꣢ ॥

(Easy to get examples by changing the last parameter in this url - https://vishvasa.github.io/devaH/hindukaH/indraH/paravastu-saama/indran-naro-nishvaset/?transliteration_target=gujarati )

Vedic literature is huge and it has a pan Indian following, being a core part of Hindu religion. Unicode standards and recommendations are clear:

U+0951 devanagari stress sign udatta and U+0952 devanagari stress sign anudatta are tone marks used in the representation of Vedic text in Devanagari. These two combining marks may also occur in the representation of Vedic texts written in other scripts, including transliterations in the Latin script. They are given the IndicSyllabic- Category value of Cantillation_Mark. (Page 476 of https://www.unicode.org/versions/Unicode14.0.0/ch12.pdf)

Devanagari Extended: U+A8E0–U+A8FF This block of characters is used chiefly for Vedic Sanskrit, although many of the characters are generic and can be used by other Indic scripts. (Page 479 of https://www.unicode.org/versions/Unicode14.0.0/ch12.pdf)

Vedic Extensions: U+1CD0–U+1CFF The Vedic Extensions block includes characters that are used in Vedic texts; they may be used with Devanagari, as well as many other Indic scripts. (Page 481 of https://www.unicode.org/versions/Unicode14.0.0/ch12.pdf)

[simoncozens]

Let's move all discussion of "adding bits of other fonts into a font" to notofonts/noto-fonts#2257.