This implements the string escaping scheme documented for the "E" (executed) and "P" (property KV) codes. This is "pure" bash and relies on no external utilities.

Although currently the only "required" escapes are backslash, semicolon, \a, and perhaps newlines, this conservatively escapes all non-alphanumeric characters.

Backslashes are doubled, non-alphanumerics are hex-escaped.

Sibling to:

• shellIntegration.fish: escape values in "E" (executed command) and "P" (property KV) codes #165631
• shellIntegration-rc.zsh: escape values in "E" (executed command) and "P" (property KV) codes #165633
• shellIntegration.ps1: escape values in "E" (executed command) and "P" (property KV) codes #165634
• shellIntegrationAddon: fix broken deserializeMessage() implementation + add tests #165635

Relates to or resolves parts of:

• Shell integration: bash and zsh don't serialize \n and ; characters #157546
• Finalize shell integration sequences #155639