fix(cloudformation-diff): string.replace error on cdk context (#2870)

`@aws-sdk/cloudformation-diff` depended on version `^2.1.1` of the `string-width`
library in `v0.28.0` of `aws-sdk`. In `v0.29.0`, the dependency was bumped to
`^4.1.0`, which inadvertently broke the `cdk context` command as reported
in: #2854.

The current version of `string-width` executes a [string replacement](sindresorhus/string-width@0bc308a#diff-168726dbe96b3ce427e7fedce31bb0bcR7), which ends up failing
when a non-string (such as the `int` row numbers of the `cdk context`
values). This did not previously occur, as the typecheck for `string`
would cause the function to return early and report zero-length.

The easiest solution here is to cast these values to `string`, which
has the beneficial side effect of ensuring that their character lengths
are taken into consideration rather than being defaulted to `0` as they
had previously been.

Fixes #2854

packages/@aws-cdk/cloudformation-diff/lib/format-table.ts

@@ -54,7 +54,7 @@ function calculcateColumnWidths(rows: string[][], terminalWidth: number): number
   terminalWidth = Math.max(terminalWidth, 40);
 
   // use 'string-width' to not count ANSI chars as actual character width
-  const columns = rows[0].map((_, i) => Math.max(...rows.map(row => stringWidth(row[i]))));
+  const columns = rows[0].map((_, i) => Math.max(...rows.map(row => stringWidth(String(row[i])))));
 
   // If we have no terminal width, do nothing
   const contentWidth = terminalWidth - 2 - columns.length * 3;