build(docs-infra): make tsconfig path detection in `switch-to-ivy` more robust (#29989)
build(docs-infra): make tsconfig path detection in `switch-to-ivy` more robust (#29989)

In light of #29926, that will change the path of `tsconfig.app.json`,
this commit switches from a hard-coded `tsconfig.app.json` path to
looking it up in `angular.json` (to be more future-proof).

PR Close #29989

shairez/angular,snaptech/angular,Toxicable/angular,mhevery/angular,gkalpak/angular,mgechev/angular,angular/angular,angular/angular,snaptech/angular,gnomeontherun/angular,Toxicable/angular,shairez/angular,Toxicable/angular,gdi2290/angular,ocombe/angular,blesh/angular,Brocco/angular,mgechev/angular,ocombe/angular,angular-indonesia/angular,StephenFluin/angular,petebacondarwin/angular,ocombe/angular,matsko/angular,sarunint/angular,gdi2290/angular,Brocco/angular,sarunint/angular,matsko/angular,manekinekko/angular,manekinekko/angular,brandonroberts/angular,IdeaBlade/angular,mprobst/angular,mlaval/angular,snaptech/angular,vikerman/angular,manekinekko/angular,vikerman/angular,alexeagle/angular,StephenFluin/angular,mgechev/angular,gdi2290/angular,angular-indonesia/angular,mprobst/angular,StephenFluin/angular,shairez/angular,vikerman/angular,sarunint/angular,brandonroberts/angular,brandonroberts/angular,vikerman/angular,mhevery/angular,brandonroberts/angular,wKoza/angular,mlaval/angular,matsko/angular,filipesilva/angular,filipesilva/angular,jasonaden/angular,brandonroberts/angular,matsko/angular,blesh/angular,gkalpak/angular,angular-indonesia/angular,snaptech/angular,mhevery/angular,petebacondarwin/angular,filipesilva/angular,alxhub/angular,gdi2290/angular,petebacondarwin/angular,gnomeontherun/angular,wKoza/angular,gnomeontherun/angular,vikerman/angular,gdi2290/angular,IdeaBlade/angular,JiaLiPassion/angular,gnomeontherun/angular,mprobst/angular,Toxicable/angular,alexeagle/angular,petebacondarwin/angular,IdeaBlade/angular,mlaval/angular,gkalpak/angular,StephenFluin/angular,alexeagle/angular,ocombe/angular,Brocco/angular,jasonaden/angular,JiaLiPassion/angular,jasonaden/angular,sarunint/angular,alxhub/angular,vikerman/angular,alexeagle/angular,gkalpak/angular,mlaval/angular,snaptech/angular,jasonaden/angular,Brocco/angular,filipesilva/angular,Brocco/angular,JiaLiPassion/angular,wKoza/angular,angular/angular,ocombe/angular,mhevery/angular,alxhub/angular,blesh/angular,IdeaBlade/angular,alxhub/angular,wKoza/angular,mlaval/angular,sarunint/angular,alexeagle/angular,jasonaden/angular,manekinekko/angular,alxhub/angular,wKoza/angular,manekinekko/angular,sarunint/angular,mprobst/angular,ocombe/angular,gdi2290/angular,StephenFluin/angular,wKoza/angular,jasonaden/angular,Toxicable/angular,alexeagle/angular,manekinekko/angular,Brocco/angular,mprobst/angular,shairez/angular,matsko/angular,mhevery/angular,petebacondarwin/angular,Toxicable/angular,filipesilva/angular,angular-indonesia/angular,petebacondarwin/angular,mprobst/angular,IdeaBlade/angular,mgechev/angular,brandonroberts/angular,mhevery/angular,blesh/angular,JiaLiPassion/angular,angular/angular,snaptech/angular,mgechev/angular,blesh/angular,shairez/angular