BREAKING: Use custom UI in snap_dialog

[GuillaumeRx]

This replaces the fields param with a content param using Snaps custom UI.

Prerequisite for MetaMask/metamask-extension#16522

[codecov-commenter]

Codecov Report

Merging #1051 (86b011b) into main (2ed41d3) will increase coverage by 1.56%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1051      +/-   ##
==========================================
+ Coverage   94.13%   95.70%   +1.56%     
==========================================
  Files         132       39      -93     
  Lines        4348     1769    -2579     
  Branches      735      292     -443     
==========================================
- Hits         4093     1693    -2400     
+ Misses        255       76     -179     

Impacted Files	Coverage Δ
packages/rpc-methods/src/restricted/dialog.ts
packages/rpc-methods/src/restricted/index.ts
packages/snaps-ui/src/builder.ts
packages/rpc-methods/src/restricted/manageState.ts
packages/rpc-methods/src/restricted/getEntropy.ts
...ments/src/node-process/ChildProcessSnapExecutor.ts
packages/snaps-utils/src/mock.ts
packages/snaps-utils/src/cronjob.ts
packages/snaps-browserify-plugin/src/plugin.ts
...kages/rpc-methods/src/permitted/invokeSnapSugar.ts
... and 83 more

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