[backport#16658] validation: Rename CheckInputs to CheckInputScripts

Summary:
3bd8db80d8d335ab63ece4f110b0fadd562e80b7 [validation] fix comments in CheckInputScripts() (John Newbery)
6f6465cefcd599c89c00f7b51f42a4b87a5ffb0b scripted-diff: [validation] Rename CheckInputs to CheckInputScripts (John Newbery)

Pull request description:

CheckInputs() used to check no double spends, scripts & sigs and amounts. Since
832e074, the double spend and amount checks
have been moved to CheckTxInputs(), and CheckInputs() now just validates
input scripts. Rename the function to CheckInputScripts().

Also fix incorrect comments.

Backport of Core PR16658

Test Plan:

ninja all check check-functional

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Subscribers: deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D8762